Pioneer RT-707 service & rebuild

[GPS16]

Hi,

the large hub reels do appear from time to time on auction sites. I have a couple of them which are 7" NAB Hubs. They are old BBC reference tapes which are IEC/CCIR spec tapes. No good for levels but I use these for Azimuth checks. A perpendicular high frequency recording is valid no matter what the level. I have used one of these reels for my MRL tape!!!

GPS16

 

[smurfer77]

I've been enjoying listening to tapes on the machine everyday... it continues to impress me. But I had not made any recordings to tape since calibration. So I decided to make a copy of some of my more valuable or collectable prerecorded tapes. I have started archiving the precorded tapes to PC using a ADC and tried and tested setup I've used for vinyl ripping. I use the Focusrite Forte which I'm very happy with. I also works as a DAC, and this is what I will use to recording my archived tapes back onto tape if desired.

So I unwrapped three sealed tapes to do a test run. Felt like Christmas. First tape I tried was a Maxwell UD 35-90 (middle), second was RMG LPR 35 (right) and the last was BASF LP35 (left). The BASF has a cool flip open box and some little tape protector plastic that I might even keep for some special tape.

I started off recording with Maxwell UD 35-90, with headphones plugged into the 707 and flipping the source/tape switch. Sounded great, very close to the source but I could hear it was ever so slightly quieter (even with the line volume pot at maximum) and with less ambiance (or maybe that was just the volume difference). Sounded good, but obviously not the same as the source.

Swapped over to the RMG LPR 35. Could not really tell the difference between the source and tape in terms of volume or character. Maybe it was slightly thinner sounding, but would need to blind test - it's really that close. Well, I did the recording setup with the LPR35 so no surprise there! Sounds fantastic.

Popped the BASF LP 35 onto the machine and got much much lower volume. This is a completely different tape to the RMG LPR35 which the machine is setup for?

I popped the Maxwell tape over onto a newly acquired Revox PR-99 that is untouched since I bought it and in need or work. Needs some high frequency adjustment, but recording sounded outstanding - disgustingly good actually. I guess there will be a PR-99 thread starting very soon.

One sad thing: I popped the LPR 35 onto the 707 again and started to record for real.... and the left channel recording level dropped several dB. I gave all switches a quick workout but nothing obvious. Demagnetized all heads. No go. So either a component went 'bye bye', or one of the record VRs just readjusted itself (I replaced the ones for playback, but not the record VRs). So the 707 is going back onto the bench tomorrow.... I do have one other little thing I wanted to do under the hood anyway. More on that soon.

 

[soundmig]

I've been enjoying listening to tapes on the machine everyday... it continues to impress me. But I had not made any recordings to tape since calibration. So I decided to make a copy of some of my more valuable or collectable prerecorded tapes. I have started archiving the precorded tapes to PC using a ADC and tried and tested setup I've used for vinyl ripping. I use the Focusrite Forte which I'm very happy with. I also works as a DAC, and this is what I will use to recording my archived tapes back onto tape if desired.

So I unwrapped three sealed tapes to do a test run. Felt like Christmas. First tape I tried was a Maxwell UD 35-90 (middle), second was RMG LPR 35 (right) and the last was BASF LP35 (left). The BASF has a cool flip open box and some little tape protector plastic that I might even keep for some special tape.

I started off recording with Maxwell UD 35-90, with headphones plugged into the 707 and flipping the source/tape switch. Sounded great, very close to the source but I could hear it was ever so slightly quieter (even with the line volume pot at maximum) and with less ambiance (or maybe that was just the volume difference). Sounded good, but obviously not the same as the source.

Swapped over to the RMG LPR 35. Could not really tell the difference between the source and tape in terms of volume or character. Maybe it was slightly thinner sounding, but would need to blind test - it's really that close. Well, I did the recording setup with the LPR35 so no surprise there! Sounds fantastic.

Popped the BASF LP 35 onto the machine and got much much lower volume. This is a completely different tape to the RMG LPR35 which the machine is setup for?

I popped the Maxwell tape over onto a newly acquired Revox PR-99 that is untouched since I bought it and in need or work. Needs some high frequency adjustment, but recording sounded outstanding - disgustingly good actually. I guess there will be a PR-99 thread starting very soon.

One sad thing: I popped the LPR 35 onto the 707 again and started to record for real.... and the left channel recording level dropped several dB. I gave all switches a quick workout but nothing obvious. Demagnetized all heads. No go. So either a component went 'bye bye', or one of the record VRs just readjusted itself (I replaced the ones for playback, but not the record VRs). So the 707 is going back onto the bench tomorrow.... I do have one other little thing I wanted to do under the hood anyway. More on that soon.

I know the feeling! I'm starting to think that I need to go completely through my deck (the way you did) because the gremlins just don't seem to want to go away.

 

[smurfer77]

I moved the 707 to the bench and realigned the recording. Typical. The weak left channel recording was gone. Must have been something with my connections or particular tape earlier yesterday. So all is fine, as it should be I suppose, after the rebuild. I did go ahead and redo the alignment while I had it on the bench anyway, partly for practice and partly to try out my Kenwood 2 channel millivoltmeter I got recently and just calibrated. Have to admit, that made the process significantly easier than using the scope or DVM. Another interesting point was redoing record bias adjustment with my other 'new' instrument.. a Leader distortion meter. An earlier post from GPS mentioned the minimization of the distortion. Was great to see the distortion swinging as I adjust bias - there is a compromise between peak recording level (signal to noise) and distortion. Anyway, old story, but nice to see with my own eyes.

Oh and the recording I just did sounded amazing. Flicking between source and recorded playback was really hard to tell any difference at all. The only give away really was the tape hiss in quiet sections.

Again, I listened via headphone, rather loudly, and for a while I paused my source music and just listened to the recorded hiss. I wanted to double check something I had checked before but just wanted to be sure of. I played with the Line Input pot at the front as I was recording and could not hear any extra hiss over the tape hiss - I don't doubt it is there, but it seems to be orders of magnitude below the tape hiss so who cares - I couldn't even measure any difference from the tape hiss as I adjusted Line Input with the millivoltmeters. On the other hand, as I adjust the Mic Input volume pot on the front, when you go past about midway you can start to hear the extra hiss, and at full it is quite significant. I suspect if you can work in the below midway region, then you are good, but if you need more gain than that you will hear the hiss and it aint pretty. I could also measure the mic hiss in recorded signal - it was ~2mV at max mic volume. Doesn't sound like much but it really stands out over the tape hiss due to the higher (compared to tape hiss) average frequency of the white noise being closer to my peak hearing response.

I don't think I will ever use the mic inputs so I'm not super worried. Maybe you can reduce hiss by swapping out transistors with lower noise versions.I'm especially not worried since if I ever used a mic level signal I have a nice external mic preamp and would never use the integrated one. But good to note: mic input is great up to midway, and rapidly gets noisy past midway. line input is not (and I don't see the point in replacing the transistors on the line input).

Next thing I'm, hopefully tomorrow, is replacing the black foam tape that is crumbling away... a small point, but I think that will be a nice finishing touch.

 

[GPS16]

Hi,

glad you have sorted the teething troubles and are happy with the results. The LP35 tape you have mentioned may be very old stock. I have a couple of those tapes and cases and I bought them when I was in my 20s I am 56 now!!!!

The LP35 will not be back coated either along with the Maxell UD.

Nice to hear the taster you have had with the PR99. Without wanting to Diss the 707, the PR99 is a whole new ball game. What do you reckon that will sound like when it has been refurbed!!!! Now do you see the FLAC references about seeing what the C270 could do!!! CDs just don't cut it!!!

GPS16

 

[smurfer77]

If you zoom in on the picture from my previous post you can see that the foam tape around the top of the chassis is crumbling away. Today I replaced the foam tape. Be careful when buying the foam tape as some of the materials used in the foams tapes starts to get gooey from about 60 C, which is not really suitable for long term in this unit as it gets warm inside. So check specs on the tape.

Here you can see I've removed the old foam tape and cleaned up with some acetone. I'm not going to lie... this took some elbow grease to remove the old tape and clean it up. I used a plastic tool and finger nails, so as not to scratch up the metal.

Here are the pics with the new foam tape installed.

On the right hand sound of the machine the servo assembly is screwed into the chassis. The original tape was one piece along this edge and you have to break the tape to get at the screws and then everything starts crumbling. In hopes of avoiding that in the future, on the right hand side I cut several piece of tape, so that when you want to remove the servo board in the future you can just remove the two little pieces over the screws and not disturb the rest. Not quite as pretty, but probably more functional in the long term.

I have enough tape to do about ten 707s so my other two 707s will get new foam tape when their turn comes. So I think all that is left is repainting the black case, and then I'm onto the other 707s. I guess i will just continue with those in this same thread. The other two 707s will not get a recap, unless I find issues, but they will be calibrated (one will be kept as a donor machine for sure) and these machines have some issues that might be more interesting than the straight up rebuild done here.

GPS, about the BASF LP 35 tape that didn't record well, that makes sense, because I'm sure I read somewhere it should be very similar to the RMG tapes (I even thought I read RMG uses the same recipe). So I will try the tape on the PR-99 just to be sure the tape is dead and I guess if the tape is no good i will do a tape dump on the PR99 and keep the reels and boxes. I actually have a couple more boxes of that...sealed. I don't have the heart to resell it if I guess it's all bad.

About the PR99, I didn't even do a 15ips record test yet. I stuck to 7.5ips to keep it as fair as possible for the comparison to the 707. That 3dB lower tape hiss sure does make a difference. Can't wait to get stuck into some 15ips. And, I assume the tapes are also less prone to dropouts, since the signal is spread over a larger tape area, right?

Anyway, the foam tape is just a little thing, but sure makes the machine look like new when you take the lid off!

 

[soundmig]

If you zoom in on the picture from my previous post you can see that the foam tape around the top of the chassis is crumbling away. Today I replaced the foam tape. Be careful when buying the foam tape as some of the materials used in the foams tapes starts to get gooey from about 60 C, which is not really suitable for long term in this unit as it gets warm inside. So check specs on the tape.

Here you can see I've removed the old foam tape and cleaned up with some acetone. I'm not going to lie... this took some elbow grease to remove the old tape and clean it up. I used a plastic tool and finger nails, so as not to scratch up the metal.

Here are the pics with the new foam tape installed.

On the right hand sound of the machine the servo assembly is screwed into the chassis. The original tape was one piece along this edge and you have to break the tape to get at the screws and then everything starts crumbling. In hopes of avoiding that in the future, on the right hand side I cut several piece of tape, so that when you want to remove the servo board in the future you can just remove the two little pieces over the screws and not disturb the rest. Not quite as pretty, but probably more functional in the long term.

I have enough tape to do about ten 707s so my other two 707s will get new foam tape when their turn comes. So I think all that is left is repainting the black case, and then I'm onto the other 707s. I guess i will just continue with those in this same thread. The other two 707s will not get a recap, unless I find issues, but they will be calibrated (one will be kept as a donor machine for sure) and these machines have some issues that might be more interesting than the straight up rebuild done here.

GPS, about the BASF LP 35 tape that didn't record well, that makes sense, because I'm sure I read somewhere it should be very similar to the RMG tapes (I even thought I read RMG uses the same recipe). So I will try the tape on the PR-99 just to be sure the tape is dead and I guess if the tape is no good i will do a tape dump on the PR99 and keep the reels and boxes. I actually have a couple more boxes of that...sealed. I don't have the heart to resell it if I guess it's all bad.

About the PR99, I didn't even do a 15ips record test yet. I stuck to 7.5ips to keep it as fair as possible for the comparison to the 707. That 3dB lower tape hiss sure does make a difference. Can't wait to get stuck into some 15ips. And, I assume the tapes are also less prone to dropouts, since the signal is spread over a larger tape area, right?

Anyway, the foam tape is just a little thing, but sure makes the machine look like new when you take the lid off!

Oh ... I see how it is. You keep me going on my 707 only to then let me know that I should have put that money toward a PR99! Dang ... now I'm going to have to look for one of those too! You scoundrel LOL - JK - no offense please.

 

[smurfer77]

The B77/PR99 seems like a really solid machine. It's just another level from what i an tell on a quick testing. But hey, nobody will take my 707 from me, except perhaps from my dead cold hands clutching onto it. It's an amazing machine and even though I say i think the revox could be a step up, the 707 has brought me more audio nirvana than... well I can't remember being this pleased and I've tried a lot of formats. I think I will always have it for 4-track purposes. Honestly, I can't believe Pioneer made the 707... no offense to pioneer, I love them, but this little machine is a miracle in build, looks and sound considering the era it was built in. Sometimes I can't believe it's a 'consumer' device when I listen to it. I have a lot of 3 3/8 and 7.5 ips 4-track tapes so the machine is going to be my main deck in many ways. But the revox is really classy, and I suspect pretty much everything about it, from build to audio components is a step up. There is a lot of big engineering points that I don't even know about yet (ask GPS!) but I notice a lot of little things. For example, it's already full of film caps. Obviously 2-track is definitely quieter, by 3dB in theory in terms of tape hiss. I'm guessing there is no hiss on the mic input on this machine too (?!) I had only played a single 2-track tape before, one I got from ebay, and it wasn't that good. So I got a shock when I did my test recording the other day. Can't wait to try 15IPS 2-track and knock another 3dB off of the tape hiss. But the reality is that the revox will just be for recording my digital music on PC to tape and maybe some of my favourite tapes ripped from the 707, unless some 15ips 2track tapes start being produced at a price I can justify.

So the 707 I guess will remain the work horse since it plays the 4tracks that I have so many of now... and even for some mix tapes I see me still using the 707, to save on tape. The 707 is now being used to record my entire 4-track collection to PC. Maybe i will build up enough tape stock to record a decent 2-track collection and that might make the PR99 more dominant.... we'll see. I still think for the moment at least, that the RT-707 could be the sexiest machine out there.

The only other machine I have my eye on now is a technics RS-1500 which records 2 track but can play 4 track as well, and it's a 3 speed machine! But I think I will sink my teeth into the PR99 first and maybe between the outstanding low speed 4 track performance of the 707 and the high speed 2 track revox i will be happy. GPS is a big fan of the revox machines btw... so I am hoping to enjoy his expertise once again when I get stuck into that beautiful beast. Having GPS16 on board has really ramped up my learning curve. I am very detail oriented and can get bogged down and having someone who knows the machine (and circuit stuff, mechanics etc etc) is a big leg up. I've just scratched the surface of tape knowledge but can you believe I knew nothing about tapes a couple of months back?!

Long story short... I'm a tape guy now. It only start early this year, but I'm hooked. It's really a big jump in listening pleasure for me that is rare. Whatever the reason is... I love it. And the reality is, the 707 low speed 4-track and the high-speed revox 2-tracks seem very complementary to each other in terms of capability. There might even be a portable r2r in my future...

 

[soundmig]

The B77/PR99 seems like a really solid machine. It's just another level from what i an tell on a quick testing. But hey, nobody will take my 707 from me, except perhaps from my dead cold hands clutching onto it. It's an amazing machine and even though I say i think the revox could be a step up, the 707 has brought me more audio nirvana than... well I can't remember being this pleased and I've tried a lot of formats. I think I will always have it for 4-track purposes. Honestly, I can't believe Pioneer made the 707... no offense to pioneer, I love them, but this little machine is a miracle in build, looks and sound considering the era it was built in. Sometimes I can't believe it's a 'consumer' device when I listen to it. I have a lot of 3 3/8 and 7.5 ips 4-track tapes so the machine is going to be my main deck in many ways. But the revox is really classy, and I suspect pretty much everything about it, from build to audio components is a step up. There is a lot of big engineering points that I don't even know about yet (ask GPS!) but I notice a lot of little things. For example, it's already full of film caps. Obviously 2-track is definitely quieter, by 3dB in theory in terms of tape hiss. I'm guessing there is no hiss on the mic input on this machine too (?!) I had only played a single 2-track tape before, one I got from ebay, and it wasn't that good. So I got a shock when I did my test recording the other day. Can't wait to try 15IPS 2-track and knock another 3dB off of the tape hiss. But the reality is that the revox will just be for recording my digital music on PC to tape and maybe some of my favourite tapes ripped from the 707, unless some 15ips 2track tapes start being produced at a price I can justify.

So the 707 I guess will remain the work horse since it plays the 4tracks that I have so many of now... and even for some mix tapes I see me still using the 707, to save on tape. The 707 is now being used to record my entire 4-track collection to PC. Maybe i will build up enough tape stock to record a decent 2-track collection and that might make the PR99 more dominant.... we'll see. I still think for the moment at least, that the RT-707 could be the sexiest machine out there.

The only other machine I have my eye on now is a technics RS-1500 which records 2 track but can play 4 track as well, and it's a 3 speed machine! But I think I will sink my teeth into the PR99 first and maybe between the outstanding low speed 4 track performance of the 707 and the high speed 2 track revox i will be happy. GPS is a big fan of the revox machines btw... so I am hoping to enjoy his expertise once again when I get stuck into that beautiful beast. Having GPS16 on board has really ramped up my learning curve. I am very detail oriented and can get bogged down and having someone who knows the machine (and circuit stuff, mechanics etc etc) is a big leg up. I've just scratched the surface of tape knowledge but can you believe I knew nothing about tapes a couple of months back?!

Long story short... I'm a tape guy now. It only start early this year, but I'm hooked. It's really a big jump in listening pleasure for me that is rare. Whatever the reason is... I love it. And the reality is, the 707 low speed 4-track and the high-speed revox 2-tracks seem very complementary to each other in terms of capability. There might even be a portable r2r in my future...

Yes, r2r is great stuff. If there were more material pre-recorded tapes, using quality tape and quality duplication (real time) techniques on HQ machines, I think there would be more of a following? I mean - even if you buy a previously re-furbed machine for say $4K ... 2 track 15 ips tapes will outperform that $20K turntable all day long! right?

REvox/Studer makes great machines. I ran across a couple in higher end studios back in the day, and they were THE machines that sounded pretty much identical to the signal that went onto them. Of course those were a few ticks above the PR99 level, but they were PRICEY!!!! If I remember correctly the big 2" 24 trackers went for around $100K back in the 1982 or so time frame. That was a bunch of money back then.

The Technics is a good machine. I mixed down an album on one of those in a small studio once - very impressive. That studio also had a TASCAM 2 track - the Technics was WAY better. I've heard that the Technics are hard to find parts for? If not, I'd snap one up if you have a shot at one - they sound great.

I did order the caps that GPS16 recommended that I replace. Maybe I'll actually get to hear my 707 running at or near spec before too long??? Ugh

 

[phantomrebel]

The Technics is a good machine. I mixed down an album on one of those in a small studio once - very impressive. That studio also had a TASCAM 2 track - the Technics was WAY better. I've heard that the Technics are hard to find parts for? If not, I'd snap one up if you have a shot at one - they sound great.
I did order the caps that GPS16 recommended that I replace. Maybe I'll actually get to hear my 707 running at or near spec before too long??? Ugh

I have some of these decks in my collection. I use the RS-1500 the most, but really like the bullet-proof RT-707. The Tascam (4-ch) sounds really good though and is great for studio work (mine came with a punch in pedal) but the heads are fairly specific so its recordings are best played back on the same deck. The Technics has been completely recapped (look for green-legged caps on these) and is quite enjoyable. I wouldn't characterize it's sound as WAY better than the Tascam however. The biggest thing to look for if you are going to acquire a RS-1500 or 1506 is to check the heads carefully as they will cost $$$$$$ to replace (intact head stacks are the hardest part to find). I admire the OP's efforts to get the most out of the Pioneer and document the process. Great job Smurf! It is a real work-horse and can sound quite good. Mine only needed a good clean/lube and some minor adjustments. They are a bargain at current prices IMHO.


As an aside, I currently have an Akai 635d in the rotation. Though it looks nice, it isn't as well built as the RT707, it feels cheap by comparison, and doesn't sound as good. It does handle 10.5" reels though.

 

[soundmig]

Nice set of tape decks phantomrebel!

 

[smurfer77]

Yeah, I've heard the Technics parts are hard to come by and the heads are pricey. Still curious if I find one in the right condition at the right price. But anyway, I've yet to see what the PR99 can do when rebuilt, and the 707 is sounding great for low speed 4-track so I'm in no rush for another machine.

Just one question about the 707 record setup. In the frequency response section 11.7 the target is -3dB (+1.5,-1.0) at 15kHz compared to 1kHz. What is the reason for the target being -3dB instead of 0dB? (achieve <-1.5dB at 15kHz can mean a fair bit of bias adjustment in my case and for now I don't understand why I wouldn't just want 0dB). Am I forgetting something in the record/play process that explains this?

 

[phantomrebel]

Nice set of tape decks phantomrebel!

Thank you, I have more, but I really wish I could find just one deck that does it all for me. Funny, I have found one turntable, one preamp, one set of speakers, but I haven't found the one open reel deck that has all the features I would like (e.g. both 2 and 4 track playback and recording, auto-reverse, record both directions, 10.5 capacity, 7.5 and 15 IPS, remote control, noise reduction, calibration tone, EE compatibility, etc.). Oh well, it is still fun to play around with the different technologies manufacturers came up with.

 

[GPS16]

Hi,
the -3dB point will be specified due to the curve of the equalisation. With the addition of the natural roll off of the tape response, if you set the 10kHz to 0dB you find a large +ve hump in the response just before it as the equalisation would be way to much to achieve 0 dB. The -3db is what keeps the response flat before it.

GPS16

 

[soundmig]

Hi,
the -3dB point will be specified due to the curve of the equalisation. With the addition of the natural roll off of the tape response, if you set the 10kHz to 0dB you find a large +ve hump in the response just before it as the equalisation would be way to much to achieve 0 dB. The -3db is what keeps the response flat before it.

GPS16

Great reminder - thanks! I'll be very happy when the day comes that I can get 10kHz on my deck to be only 3dB down. I ordered some caps, so we'll see if those do the trick

 

[smurfer77]

Okay, so for the rebuilt machine I'm still going to repaint the black case. But that's about it for now.

So..... onto the second RT-707 (I have 3 in total). It's meant to be a donor machine for the rebuilt beast, to see me through to my old age, but I would like to get it running perfectly and calibrate it, etc. The second machine is a very clean unit. In fact, I took the face plate from it and put it onto the rebuilt machine. It also has almost new heads. There is a bit of wear but it's barely worth mentioning.... not bad for a 2nd hand shop bargain. Okay so here is the present list of issue:

- Left channel cuts out occasionally. SOURCE switch issue. Has been cleaned/exercised but still plays up sometimes.
- needs playback calibration. FWD direction left balance/EQ seem way off.
- record untested.
- On FWD playback the motors stop when tape runs out, but on REV playback the reels keep spinning when the tape runs out. So that isn't just an issue of the tape detector spring right? It seems to move okay, and that would affect both directions right? Although I do notice that while it stops in FWD direction, it does take about 3 seconds before it happens.
- pinch roller not that grippy. When leader tape is running through the tape often jumps out from between the capstan and the pinch roller. Have tried clean and rubber rejuventator. Sand paper next? Or just buy a new roller?

That's it though. Other than these things it sounds pretty good and I'm not expecting an major dramas with calibration.

 

[smurfer77]

Great reminder - thanks! I'll be very happy when the day comes that I can get 10kHz on my deck to be only 3dB down. I ordered some caps, so we'll see if those do the trick

You will get there! And I'm telling you, it's worth it. Listened to tapes all day and can't stop. Sounds like you have played with some fancy units during your work, but I reckon the 707 will put a smile on your face when you have it aligned.

 

[GPS16]

Hi,

Some suggestions.

- Left channel cuts out occasionally. SOURCE switch issue. Has been cleaned/exercised but still plays up sometimes.
Check the pot on the rear panel. It is one which gets forgotten. Run it from end to end and then back to the indent.

- On FWD playback the motors stop when tape runs out, but on REV playback the reels keep spinning when the tape runs out. So that isn't just an issue of the tape detector spring right? It seems to move okay, and that would affect both directions right? Although I do notice that while it stops in FWD direction, it does take about 3 seconds before it happens.
Check that the wire loop drops at end of tape in reverse. Does the machine clunk when the stop solenoid gets pulsed?? Do the pinch rollers drop?? 3 secs is a bit excessive for the wire loop damping. As the loop is being shoved in the other direction during reverse play it may not be dropping. Either way, looks like the damping fluid needs attention. It could be drying up.

- Pinch Roller not that grippy. When leader tape is running through the tape often jumps out from between the capstan and the pinch roller. Have tried clean and rubber rejuventator. Sand paper next? Or just buy a new roller?
This can be due to the roller but it can also be due to the tape take up tensions being out of spec during play modes. The large green resistors may need attention. Remember that the reel motors have 4 power settings. 1-Full bore. 2-Fwd Play Tension. 3-Rev Tension. 4-Fastwind Back Tension. The last 3 need to be in the ranges set by the procedure in the manual. If the roller is barrel shaped then it needs refurb.

See what you find.

GPS16

 

[soundmig]

You will get there! And I'm telling you, it's worth it. Listened to tapes all day and can't stop. Sounds like you have played with some fancy units during your work, but I reckon the 707 will put a smile on your face when you have it aligned.

Thanks for the encouragement. I'm sure it will sound good. I can get the EQ mostly in spec via the REV playback head (with extreme adjustment) and that sound very good. So, I have "hope" that I'm getting close. Sounds like your having some transport issues - I'd be really lost there - ugh. On mine, GPS16 said something in one of his posts that really resonated with me. It was about C128 (C127 also I assume) and that if it was bad some circuit may not be turning on. This totally makes sense as it is "as if" the EQ section simply isn't functioning properly - plus, one time I did have plenty of high frequency for a short run- then it went away. I would think that a bad or leaky cap might lead to such a situation? So, we will see.

 

[smurfer77]

Hi,

Some suggestions.

- Left channel cuts out occasionally. SOURCE switch issue. Has been cleaned/exercised but still plays up sometimes.
Check the pot on the rear panel. It is one which gets forgotten. Run it from end to end and then back to the indent.

- On FWD playback the motors stop when tape runs out, but on REV playback the reels keep spinning when the tape runs out. So that isn't just an issue of the tape detector spring right? It seems to move okay, and that would affect both directions right? Although I do notice that while it stops in FWD direction, it does take about 3 seconds before it happens.
Check that the wire loop drops at end of tape in reverse. Does the machine clunk when the stop solenoid gets pulsed?? Do the pinch rollers drop?? 3 secs is a bit excessive for the wire loop damping. As the loop is being shoved in the other direction during reverse play it may not be dropping. Either way, looks like the damping fluid needs attention. It could be drying up.

- Pinch Roller not that grippy. When leader tape is running through the tape often jumps out from between the capstan and the pinch roller. Have tried clean and rubber rejuventator. Sand paper next? Or just buy a new roller?
This can be due to the roller but it can also be due to the tape take up tensions being out of spec during play modes. The large green resistors may need attention. Remember that the reel motors have 4 power settings. 1-Full bore. 2-Fwd Play Tension. 3-Rev Tension. 4-Fastwind Back Tension. The last 3 need to be in the ranges set by the procedure in the manual. If the roller is barrel shaped then it needs refurb.

See what you find.

GPS16

Thanks GPS. The sage continues. Will look into the points above, probably on sunday.

BTW, I threw that old BASF tape onto the PR99. Recorded no problem. Put it back onto the 707 and kind of sounded okay on one channel, weak on the other.