Technical help with a Pioneer RT- 707 Please

[Sam Burden]

Hi I have an RT-707 that works great with one exception if it is powered up and idle if I turn the volume way up on my amp it produces a motor boating sound. It plays fine and sounds good otherwise. During play I havnt noticed a problem. I believe its a cap issue because if my amp is volume is up and I power up the Pioneer there is a very slight delay before it starts as if the caps are charging and then once charged it starts. If I turn my volume down on my amp to what would be a normal volume level you cant hear it. Question is has anyone ran into this and if so was it filter caps? Or what? Its not my amp its dead quiet when in use and on a different component, cd, phono etc. It only happens once the RT is powered up. There is a 102 electrolytics in this beast and I am not interested in total recapping of the unit as I do not want to change the sound signature. I dont have a problem with putting high grade filter caps in or changing a problem one but would like to know if anyone else has run into it before I do anything. Thanks Sam

 

[markthefixer]

There are plenty of muting circuits in there, and just for grins I checked for the failure prone CSSA caps, and there are only three, in the servo control (speed) circuits. All three are 0.1uf and are cascaded RC filters. C909, C910, C911.

You need to have someone try to duplicate what you are addressing, with another RT-707 to see if it happens on other units.

Changing the sound will only happen when things deteriorate, and putting them back to spec is just restoring the sound you should have.

 

[Sam Burden]

There are plenty of muting circuits in there, and just for grins I checked for the failure prone CSSA caps, and there are only three, in the servo control (speed) circuits. All three are 0.1uf and are cascaded RC filters. C909, C910, C911.

You need to have someone try to duplicate what you are addressing, with another RT-707 to see if it happens on other units.

Changing the sound will only happen when things deteriorate, and putting them back to spec is just restoring the sound you should have.

Thanks Mark, I will replace those and check the filter caps.

 

[soundmig]

A recap of my servo board made a difference in the performance of my RT-707. I didn't know those caps were prone to failure - so it now makes sense why that helped my machine

 

[Sam Burden]

A recap of my servo board made a difference in the performance of my RT-707. I didn't know those caps were prone to failure - so it now makes sense why that helped my machine

Thanks for the reply, I have made a list of the electros on the servo board and am going to recap it along with the two mains, the motor runs and the power filter caps. That should keep it running a long time. One other question I see the the small holes on the back of the reel motors. I assume these are oil holes for the bearings? I have some 3 in 1 motor oil and also some liquid bearings which is 100% synthetic any suggestions as to which is best as well as how much? Service manual has no reference whatsoever on that. Thanks Sam

 

[Sam Burden]

There are plenty of muting circuits in there, and just for grins I checked for the failure prone CSSA caps, and there are only three, in the servo control (speed) circuits. All three are 0.1uf and are cascaded RC filters. C909, C910, C911.

You need to have someone try to duplicate what you are addressing, with another RT-707 to see if it happens on other units.

Changing the sound will only happen when things deteriorate, and putting them back to spec is just restoring the sound you should have.

Hi Mark, sorry to bother you. I was looking at replacing the 2 main filter caps which are 2.5uf 250v and a 6.8uf. The 6.8 is readily available not so on the 2.5. What you replace it with a 2.2 or a 3.3 or would you go with something different? Same question on the motor runs ones a 5.5 uf and a 4uf both 250v. Not finding those at all. I ordered all the caps for the servo and power boards. I am going to use Elna Silmic ii, I recapped my Marantz 1060 with these and was very impressed with the sound. One more question there is a small hole on the two reel motors near the bearing is this an oil hole? The service manual does not address lubrication at all. If so how much should I put in. I have liquid bearings synthetic as well as superlube syn and 3in1 motor oil.so am open to whatever. Thanks for your time. Sam

 

[markthefixer]

Caps come in standard values, BUT some of the old caps in these had huge tolerance ratings, as much as +80% and -20%.

Those motor caps are something quite different than little electrolytic caps, they are probably metal sealed bodies that are oil filled and rarely go bad. The listing in the BOM isn't helpful, as they are custom Pioneer numbers. I have checked their parts site to no avail. Pictures would be VERY helpful.

I don't work with tape decks anymore, and am unfamiliar with motor lubrication on those motors.
The users manual ALSO does not address lubrication.

But the electronic caps, I am very familiar with, and they can be quite particular in their replacements, which is why I encourage lists that show the model, board #, capacitor # and BOM details that reveal the necessary details - INCLUDING whether or not a particular cap has special considerations - the wrong choices in the past revealed themselves to me by INCREASED background noise.

 

[Sam Burden]

Caps come in standard values, BUT some of the old caps in these had huge tolerance ratings, as much as +80% and -20%.

Those motor caps are something quite different than little electrolytic caps, they are probably metal sealed bodies that are oil filled and rarely go bad. The listing in the BOM isn't helpful, as they are custom Pioneer numbers. I have checked their parts site to no avail. Pictures would be VERY helpful.

I don't work with tape decks anymore, and am unfamiliar with motor lubrication on those motors.
The users manual ALSO does not address lubrication.

But the electronic caps, I am very familiar with, and they can be quite particular in their replacements, which is why I encourage lists that show the model, board #, capacitor # and BOM details that reveal the necessary details - INCLUDING whether or not a particular cap has special considerations - the wrong choices in the past revealed themselves to me by INCREASED background noise.

Thanks Mark, I will take photos of the caps. The two other ones are not on a board they look to be main power caps and are just below the servo board. Replacing the motor run caps was suggested by someone who had one go bad. But my unit does work fine. So maybe I should look at replacing the two power caps and leave the motor runs alone. Again someone else on another site had stated that the 2.5 uf main was a common failure. Thanks for your time. Sam

 

[Sam Burden]

Thanks Mark, I will take photos of the caps. The two other ones are not on a board they look to be main power caps and are just below the servo board. Replacing the motor run caps was suggested by someone who had one go bad. But my unit does work fine. So maybe I should look at replacing the two power caps and leave the motor runs alone. Again someone else on another site had stated that the 2.5 uf main was a common failure. Thanks for your time. Sam

Here is a screen shot of the service manual showing the caps below the board

 

[Sam Burden]

Thanks Mark, I will take photos of the caps. The two other ones are not on a board they look to be main power caps and are just below the servo board. Replacing the motor run caps was suggested by someone who had one go bad. But my unit does work fine. So maybe I should look at replacing the two power caps and leave the motor runs alone. Again someone else on another site had stated that the 2.5 uf main was a common failure. Thanks for your time. Sam

Ok found them by going through the different parts list turns out they are part of the servo board assy although not actually on the board and are metallized paper caps. Here is a photo of the servo parts list. They are c921 and c922. So Then electros would not be appropriate in their place right? I would need to go to a film cap? Heres the list.

 

[Sam Burden]

Ok found them by going through the different parts list turns out they are part of the servo board assy although not actually on the board and are metallized paper caps. Here is a photo of the servo parts list. They are c921 and c922. So Then electros would not be appropriate in their place right? I would need to go to a film cap? Heres the list.

Mundorf makes mkp caps which are metalized polypropylene caps . Would these be a good replacement? They have a 2.7uf 250v and a 6.8uf 250v both of which are audio grade caps. Thanks again.

 

[markthefixer]

I don't yet know - have to consider HEAT in these caps. You've done a lot of legwork but I'm too dead on my feet to dig in and think straight. I'll have to come back to this.

 

[BobbyN]

Hi I have an RT-707 that works great with one exception if it is powered up and idle if I turn the volume way up on my amp it produces a motor boating sound. It plays fine and sounds good otherwise. During play I havnt noticed a problem. I believe its a cap issue because if my amp is volume is up and I power up the Pioneer there is a very slight delay before it starts as if the caps are charging and then once charged it starts. If I turn my volume down on my amp to what would be a normal volume level you cant hear it. Question is has anyone ran into this and if so was it filter caps? Or what? Its not my amp its dead quiet when in use and on a different component, cd, phono etc. It only happens once the RT is powered up. There is a 102 electrolytics in this beast and I am not interested in total recapping of the unit as I do not want to change the sound signature. I dont have a problem with putting high grade filter caps in or changing a problem one but would like to know if anyone else has run into it before I do anything. Thanks Sam

Is there a noise difference between "source" and "tape"?

 

[Sam Burden]

Is there a noise difference between "source" and "tape"?

Yes there is. When it's out I get the clicking sound when it's in it's more of a white noise. I am using the din cord between the amp and reel. I tried it with rcas instead of the din cord and its the same using either one.

 

[Sam Burden]

I don't yet know - have to consider HEAT in these caps. You've done a lot of legwork but I'm too dead on my feet to dig in and think straight. I'll have to come back to this.

Hello, I checked out the Mundorfs they are rated at 105 degrees. No temp markings on the ones installed.

 

[markthefixer]

I tried to find them, ran out of time - WHERE are you looking??? Part number? site? these are similar to ceiling fan capacitors if i am correct.

 

[BobbyN]

Sam, I had the white noise problem with mine one time. There was a noisy transistor on the mic amp board. It's been quite a while but I do remember there were six identical transistors on that board and one of them caused the white noise. It sounded like someone left the hose on outside. I replaced all six.

Not sure if that could have anything to do with your "clicking" sound but I thought I'd mention what I had found in the past. Also that noisy transistor tested fine on a transistor tester.

Hope this can help.

Keep us posted.

Bob

 

[Sam Burden]

Is there a noise difference between "source" and "tape"?

Sam, I had the white noise problem with mine one time. There was a noisy transistor on the mic amp board. It's been quite a while but I do remember there were six identical transistors on that board and one of them caused the white noise. It sounded like someone left the hose on outside. I replaced all six.

Not sure if that could have anything to do with your "clicking" sound but I thought I'd mention what I had found in the past. Also that noisy transistor tested fine on a transistor tester.

Hope this can help.

Keep us posted.

Bob

Thanks Bob, I will look at replacing those just got my caps in from Mouser for the power supply and servo boards so will start with the power supply first and see if I can eliminate it and let you know when I get it resolved. It could very well be in those transistors possibly a combination of them. One question for you since you own one. There is what appears to be an oiling hole on the back end of the reel motors but I cant seem to find a reference to oiling them. Do you know if they are oiling holes ? Thanks Sam

 

[Sam Burden]

I tried to find them, ran out of time - WHERE are you looking??? Part number? site? these are similar to ceiling fan capacitors if i am correct.

We might have our wires crossed, at this point I am nt going to worry about the motor run caps. I am looking to replace the two metalized paper caps in the servo assy. They are 2.5uf 250v and 6.8uf 125 volt. I have found Mundorf MKP metalized polystyrene caps from Parts Connexion which are 2.7uf 250v and 6.8uf 250v rated at 105 c. Dont see why these would not work but I am not an audio cap expert so not sure. On the reference sheets they are calling them MKP caps in their Mcaps series. Thanks EDIT after reviewing the schematics I realized there are four motor run caps in this unit with ones marked left and right which I am not going to replace as well as the two that are in the servo board list which I had thought were main power filters based on a post on another sight. My mistake for not looking at the schematics sooner. That post had stated that the 2.5uf was known to fail. However I am not seeing that elsewhere and what I do see is that those two in the servo circuit can affect the motor speeds so I am going to leave those alone also.

 

[BobbyN]

Thanks Bob, I will look at replacing those just got my caps in from Mouser for the power supply and servo boards so will start with the power supply first and see if I can eliminate it and let you know when I get it resolved. It could very well be in those transistors possibly a combination of them. One question for you since you own one. There is what appears to be an oiling hole on the back end of the reel motors but I cant seem to find a reference to oiling them. Do you know if they are oiling holes ? Thanks Sam

Sam, Sorry it took so long for me to get back to you. I'm not sure about the oil for the motors.
Bob