HELP! I am so depressed....

[analog addict]

Since I heard arcing (http://www.audiokarma.org/forums/showthread.php?t=186151) in the rectifier of my 2nd EICO HF-20, I figgered I needed to rebuild the power supply caps, even though they measured OK on my cap meter. Well, I did so last night, and also de-oxited and Fader lubed all the pots. I let every thing dry over night, compared the wiring to the 1st one I redid, which seems to be working fine (so far), and brought both downstairs to fire up. I set my variac at 100 VAC, and turned them on after hooking up a source and speakers....

I thought I heard a faint little crackle from the rectifier immediately after start up, but I wiggled the tube and didn't see any discharge, but after maybe 5 or 6 seconds.... *POOF*....:yikes:

A sound like a pop and a cloud of smoke seeping out from underneath the amp....!!$%#!@#%&!!!...:rant:....:cry:

I turned it off, and flipped it over to see if I could spot any smoked components...Nothing obvious, so I looked a little more carefully, and spotted some brownish oily residue on one of the new caps, but it measured OK with my cap meter.....:dunno: I hope it isn't the power transformer, although the fuse looks OK

I have sunk so much time into these amps, and just can't seem to get them right, and now this. Sometimes I wonder if I'm wasting my time or biting off more than I can chew....

Anyone have any ideas on what I should do next????...:worried:...:sigh:

[spaceman]

Well, I don't have any good advice, but can offer my sympathy. That must be pretty frustrating. :sigh: Good luck.

[bowtie427ss]

Sorry to hear of your troubles Allan, if it's any consolation i haven't found myself well enough yet to try and figure out my current tube dilemma.

You didn't put a cap in backwards(reversed polarity) by any chance did you?

Only advice i can offer at this point is to just eliminate the simplest possibilities first.

Hang in there, take a break from them if need be, but NEVER give up.

[thisOne]

Anyone have any ideas on what I should do next????...:worried:...:sigh:

:beer::beer::beer:

[Bill H]

If your cap went POOF.... I doubt it would keep the same value and prolly start to bulge. All I can say is go piece by piece and check every value, preferably out if circuit. I also doubt it was your tranny. I can't say I've seen one of them smoke unless it's been beaten on for quite some time.... :D

Best of luck! Hope it recovers quickly!!

[sloober]

Hey I'm in Apex, not far from you. Perhaps I can help. Shoot me a PM and we can talk.
John

[bricktop]

Take a pic of the underguts. Maybe something will stick out to one of us. :scratch2:

[cableguy]

Dam Allen....sorry man

[analog addict]

Here are some pix....

http://www.audiokarma.org/forums/attachment.php?attachmentid=112543&d=1223777545

http://www.audiokarma.org/forums/attachment.php?attachmentid=112542&d=1223777545

The cap that had the residue is the furthest to the left. All caps are - side to ground through the center grounded terminal....

Micah, sorry I haven't responded to your PM. It's exactly this sort of thing that has me hesitating. I'm still thinking though...

John,
Homer/Rich says he's spoken to you and that you seem to be able to navigate your way around a piece of tube gear. I've been thinking of begging Jay in Kansas to take a look at this thing, but some local help would be even better. I might actually learn something.

Here's a schematic for reference....

http://audiokarma.org/forums/attachment.php?attachmentid=56998&d=1186622564

I have different one if anyone's really interested

If anyone sees anything, please let me know....I'm gonna vent my frustrations by wasting a bunch of aliens on HALO 2...

[bricktop]

It looks, though I can't be sure, is that 6kohm, 10W resistor connected from pin 8 of the rectifier to ground?

Also, the cap right after the rectifier (39uF, 450V) is pretty close to it's rated voltage @ 450VDC. That may be why it snapped before after shortly getting to full line voltage, especially with line voltages higher these days. That might be a better spot for a 600VDC cap, like a sprague atom.

[gogofast]

i'm not even close to being an expert or qualified to give you advice, but i've had similar experience when i hooked up an electrolytic in wrong direction or one of the lead to a wrong place..... almost happens immediately. if the other one's wiring is exactly the same...i think there's a chance that might be the case. is the cap new or is that NOS? also that area seem kinda crowded...might wanna use shrink tube to make sure nothing's touching each other.

[targeteye]

I do feel for your delema but something you mentioned didn't seem right. "I set my variac at 100 VAC, and turned them on after hooking up a source and speakers...." The variac set to 100 isn't going to help you at all. Whenever bringing a piece of equimpent up after repair or modification you should start at 0 and bring it up slowly. You should also have a current meter in the circuit so you can get see if it starts pulling excessive current.

Just trying to help you save headaches in the future.

Steve

[cademan]

It could be just the way the camera took the picture, but the cap coming off of the rectifier (the little blue one to the right of the 39MFD @ 450V) looks to be backwards. It looks like the negative side of the 39MFD is connected to the same side the positive of the little blue one is connected to.

[sloober]

Hard to tell from the photos. But if you want, I can take a look for ya. I have re-built an HF-60 and Eico gear is pretty easy (compared to my Sansui anyway) Shoot me a note and I will be glad to come by and have a look. 1 thing I have found...step away for a while. A clear head will go along way.
John

[EchoWars]

Bit of advice: Quit using those crappy Xicon caps.

[twc5964]

Bit of advice: Quit using those crappy Xicon caps.


Agreed with Echowars ! Also,it is possible if the orientation of the cap is correct-it could have been a bad or weak capacitor from the beginning.I know cause I've had this happen before.Try another cap and see what happens.

[Kenny]

Check and recheck those caps!!My tech has had more than one brand new cap go bad so its not uncommon anymore,and after our Eico ST-40 adventure just about everything is now new.Go with the better known caps,with higher values because of higher voltages,wait and save up if you have too,good parts are worth it in my opinion,I mean you are going to all the trouble to restore it,you want it to last and sound half ways decent,you don't have to go ultra high end,something in the middle is fine,the orange drops have a great reputation,I'm sure there are many others if you ask the techs here,find something suited to your musical preferences.Please don't get discouraged,my tech has been trying to troubleshoot my Eico ST-40's pre-amp section now as it has a loud hum that increases with volume that has him stymied,for about 3 weeks of evenings/weekends so far!.The power amp supply section is dead quiet now,I used it briefly as an amp,for a week or so,but it was totally Blah without its own pre-amp 'Magic'.After finding the bad(new)cap,that ceased the motor boating issue,and re-routing some 'new' wires quieted things down even some more,then surprise,a bad wire to his test bench speakers,it was giving a buzz,he bumped it with is elbow and it stopped,so don't overlook the obvious.I gave him some new test bench speakers,and we chucked the other crap.In our Eico journey of discovery we also had to replace a hanging by a thread output transformer.Took over a month and a half to find one of those,and I was just plain lucky another Canuck Audio member helped us out,or else it was going to be new one from Heyboer.He was at it for at least a month,before the output tranny went kaput!.Between that,the motor boating issue,intermittent buzzing in the speaker,I'm surprised he didn't throw it against the basement wall,but he is a good tech and has not given up,he is coming back to it,one more time.It now sounds absolutely stunning,nice Big Phat warm Bass Drum,very surprisingly good detail,sweet mids,we used orange drop caps......too bad though its only through one channel,mono anyone,lol.I like it way better than my Eico ST-70 through my Altec 19's.The Eico St-70 has too much gain with the Altec 19's.Sounds excellent with its new auricaps when now played in my secondary system through some Tannoy Reveals..Please don't give up,be patient,take your time,stay focused,you "will "solve this problem.We have temporarily parked this ST-40 for a few weeks,work schedules,family obligations,then he is going to rip down the right channel pre-amp section,going over it AGAIN!..He has never had an Eico like this one!!!.And he has done pretty much all of them over the years...I swear this particular ST-40 been a battle right from when it arrived on my doorstep from Nova Scotia with the cage sticking out of the box.Ouch!!..Bad tubes,bad tranny wire,gee there's a surprise considering the crappy packing job,wrong rectifier tube,absolutely filthy dirty,chassis,I could go on and on,but you get the picture.It looks/sounds great now!!.When reflecting on this one I am beginning to think it was dragged up inside one of their cod nets and resold after it dried out!! I am absolutely not giving up on this amp!Not after what we have been through so far.Sooner or later,some one will find this hum out.Everything else has been pretty much replaced with new tubes,tube sockets caps,wiring, RCA jacks,speaker connectors,Input switch,etc.The original volume pot has been ruled out as the problem,and its in the pre-amp section right channel for sure? He is going to have a other go at it,he is not a quitter,and if he has no luck my other tech friend says he will have a look see.Sometimes another set of eyes can spot something right away after you have been chasing your tail for weeks/months.It will be worth it.These old amps sound so Fine when they are brought up to new specs,and are worth the time/effort/money in my opinion.You 'Will' find the problem!..It has to be something!!..Good Luck,be thorough,check 'everything' other helpful Audiokarma Folk have spotted as possible trouble causing congested areas,backwards wiring,bad grounds,bad solder joints,it certainly doesn't take much to throw things out of whack.The nice thing about many Eico's is they are usually a fairly roomy chassis.Please post when you find out what caused the problem,just think how much it would help some else out down the road!!..Peace & Harmonies..Altec Triode Concert Kenny

[kvflyer]

I know it has been said before but here goes again, short post.

First, be absolutely sure that the electrolytic capacitor is connected correctly, + to +. The negative does not always go to ground/chassis. eg. bias circuits.

Second, make sure the capacitor voltage is rated higher than the actual voltage applied to it. Remember that the B+ will be higher until all of the tubes are conducting.

Third, yes, some new stuff is not always good. I won't be a hypocrite and tell you that I always use Sprague Atom eletrolytics but they are good, albeit more expensive.

Let us know!

[jaymanaa]

It could be just the way the camera took the picture, but the cap coming off of the rectifier (the little blue one to the right of the 39MFD @ 450V) looks to be backwards. It looks like the negative side of the 39MFD is connected to the same side the positive of the little blue one is connected to.

That's what I see too.:scratch2:

[analog addict]

It could be just the way the camera took the picture, but the cap coming off of the rectifier (the little blue one to the right of the 39MFD @ 450V) looks to be backwards. It looks like the negative side of the 39MFD is connected to the same side the positive of the little blue one is connected to.

These little caps are not marked as well as the radials. I was assuming that the black end was the negative terminal. Since the "-" strip was black and seems to point in the direction of the black end, I assumed it was the negative end. Am I mistaken? I'll have to double check my other amp, but IIRC, it's the same orientation I used in it.

Also, the 6KOhm lead goes to the 1st 20uF stage, the lead kinda swings backwards....

[cademan]

On that axial capacitor, if it is indeed polarized, the indented end is the positive side.

[analog addict]

Well, I took a big breath, and plugged in the (de)soldering iron....Took apart the ground connection for that cap cluster, and found that the little cap is reading about 1/2 it's value. It was a 1.0uF to try and bring the 39uF cap closer to 40uF, since the 39uF cap measured about 37.5uF to start with. However, I think I will leave it out and try again, this time with the amp upside down so I can watch it more closely.

I thought that since these were new caps, and the amp had recently spent time at 110VAC, it would be safe to star at 100 VAC. What would be a safer method of starting it up? Go all the way down to 40 VAC? 90VAC? How long should I stay at each voltage? Is it OK to run the amp upside down? I know some amps were designed with this in mind, but this one obviously was not....:scratch2:


Oh and one last question about the small caps. One end has a shiny metal end plate with an extra "button" of metal around the junction of the end plate and the wire. The other end is black with the wire coming out of a little hole, with another small hole nearer the edge of the end plate.

For the record, which end is the negative terminal????

Thanks for all your help guys.....:thmbsp:

BTW, one more thing....Where should I put the ammeter in the circuit to watch the current?

[jaymanaa]

The shiny aluminum end is negative while the black plastic (insulated) end is positive.:thmbsp:

[analog addict]

The shiny aluminum end is negative while the black plastic (insulated) end is positive.:thmbsp:

Gee, think that's why smoke came pouring out of it.....:stupid:

Now I'm wondering why the other one hasn't gone up in smoke...:scratch2:

Let me ask a general 5u4 question. It's my understanding that 40uF is about the limit for the 1st stage of a power supply circuit with this tube. What changes if I leave the circuit with a 1st stage of say 37.5-38uF? Less WPC? More ripple in the DC? Anything?

[NYListens]

Couldn't you use a non-polarized film cap in place of that lytic anyway?

[jaymanaa]

37 or 38 uf will do just fine:yes:

[analog addict]

Cut the 1uF cap out of the other amp. I guess since I ran up the voltage on that one gradually, it must have gently tunneled a hole through the dielectric material, cause when I measured it on the cap meter, it read .025uF...:D

Anyway, the amps are upside down on the kitchen table at 60 VAC. I'll run them up 10VAC every 10-15 minutes and see what happens. So far no smoke, no sizzling, and filament glow on all the output tubes, so I'm hoping I'm in business.

Thanks for bearing with me when I felt overwhelmed....:thmbsp:

[Fast_Eddie]

Cut the 1uF cap out of the other amp. I guess since I ran up the voltage on that one gradually, it must have gently tunneled a hole through the dielectric material, cause when I measured it on the cap meter, it read .025uF...:D

Anyway, the amps are upside down on the kitchen table at 60 VAC. I'll run them up 10VAC every 10-15 minutes and see what happens. So far no smoke, no sizzling, and filament glow on all the output tubes, so I'm hoping I'm in business.

Thanks for bearing with me when I felt overwhelmed....:thmbsp:

Fingers crossed!

Sounds like you may have it. Congrats! As simple as it all seems on paper and in your head, when you're actually in there with the soldering iron trying to get the right cap in the right place, it's easy to make a mistake.

But I have to say, reading your story got me jonzin' to find another tube amp to recap and enjoy.

Take care,

Ed

[andy]

I generally don't go that slowly with a variac. The idea is to just ramp the power up over maybe 10 seconds to a minute rather than slamming it with 120v. You can watch and listen for signs of trouble, and abort at any time. It saves a lot of smoke and flames when something is seriously wrong. Using a current meter is a very good idea.

I avoid running things at low voltage for too long because it can cause damage (for example, a short might not blow the fuse at 60v, but it can burn out the transformer if it's left to sit for a long time.

[analog addict]

Got 117 VAC running through the amps now, and I have sound from both. The amp that went up in smoke functions perfectly now, but the other amp doesn't have anywhere near as much gain, and sounds "thin". No effect from turning the Bass and Treble controls either....:scratch2:

However, at least I have 2 essentially functioning amps now....:banana:

[gogofast]

But I have to say, reading your story got me jonzin' to find another tube amp to recap and enjoy.

Ed

i feel the same way....aren't we SICK??!!

[gogofast]

Got 117 VAC running through the amps now, and I have sound from both. The amp that went up in smoke functions perfectly now, but the other amp doesn't have anywhere near as much gain, and sounds "thin". No effect from turning the Bass and Treble controls either....:scratch2:

However, at least I have 2 essentially functioning amps now....:banana:
do all the tubes check out ok?

[analog addict]

do all the tubes check out ok?

I checked them all before this last stage of the rebuild. I suppose I could switch one amp's tubes to the other though....

I'm guessing it's something in the controls/circuitry though....:sigh:

[cademan]

:D Now it's time to check the wiring or resistors in the tone control circuit. It sounds like the tone circuit is not getting any power and the amplifier is running flat. :yes:

[analog addict]

:D Now it's time to check the wiring or resistors in the tone control circuit. It sounds like the tone circuit is not getting any power and the amplifier is running flat. :yes:

And the nice thing, as with all monoblock sets, I have a working example to use as a blueprint....

Back on track and feeling a lot less sorry for myself.....:thmbsp:

[bricktop]

At full input voltage, might wanna get a meter and check the voltage across the 39uF, 450VDC cap (first stage). I have a sneaky feeling it is a bit above its rating. For the long term, probably should get higher voltage rated caps for that. :scratch2:

[analog addict]

http://photos-f.ak.fbcdn.net/photos-ak-sf2p/v355/27/44/1316738/n1316738_34055173_8073.jpg

Chinese 6L6's and 4312c's actually. Never heard these speakers sound so good...:sing:

Listening to a SONY STC-7000 tuner via tape out to a modded BH Foreplay II with RCA cleartops on board. Then to the HF-20's......
Disconnected the pre amp from the power amp and bummin' about all the work done on the preamp section....but not bummin much.....:D

WOW!.....:thmbsp:......:music::music::music::music :

RCA 6L6 Blackplates and cleartops all around tomorrow. Time to get serious with the K-Horns.....:smoke:

[vinyldavid]

Great job!

I know that I need to get my one Eico back out and see what I can do with it.

[HomerJSimpson]

Glad you are enjoying them...:thmbsp:

[sloober]

Eico made some great stuff. Glad they are working. Someday I need to get another HF-60 so I have a pair. Enjoy!
John

[wajobu]

Good help here...nice thread...patience and thoughtful analysis...wonderful things.

[Kenny]

Its great to hear you figured out the problem with a little help from the Audiokarama tech friends!.Perseverance always pays off,but it sure doesn't hurt to park em briefly,take a breather,and a few drinks or bustin a little Alien ass doesn't hurt either!..Man they can be frustrating can't they!.Mono is nice to have a model to compare to,just like me doing a brake job on the car,having another one to compare to sure helps proper assembly.I have never got to listen to a Bottle head,but seems everything I have read about them is very Positive and I bet thats a a real sweet sounding combo.Midrange to die for!.Almost scored a Bottlehead a few years back but couldn't come up with the other hundred.I always wanted a pair of HF-20's like that,that amount of power seems to suit me & my Altec 19's just fine.The 20's don't seem very common up here in Canada,lots of HF-81's and HFT-90 tuners though.My tech just picked up my Eico ST-40 after a breather to have another go at it to see if he can get the hum out of the right channel pre-amp? I am so hoping he can figure it out,its sounds so good in the one channel thats not humming!Triode Altec Concert Kenny

[analog addict]

Good help here...nice thread...patience and thoughtful analysis...wonderful things.

Now the fun begins. As soon as the wife gets out of bed, the tube rolling starts. I found 6 Mullard 12AU7's, so both amps and the BHII get some english vacuum magic, along with the RCA outputs. Here's a picture with the lights on....

http://www.audiokarma.org/forums/attachment.php?attachmentid=116699&d=1226162325

Anyone have any ideas where I can find an OEM knob????....:scratch2:

[jaymanaa]

Hey! Finally a good use for SS gear..................................stack tube stuff on it.:D (just kidding) How about a pic of the knob you need? I have a couple drawers full I could check.

[analog addict]

How about a pic of the knob you need? I have a couple drawers full I could check.

Your wish is my command O Gracious One! How about two?

http://www.audiokarma.org/forums/attachment.php?attachmentid=116704&d=1226163902

http://www.audiokarma.org/forums/attachment.php?attachmentid=116705&d=1226163902

The ironic thing is only two of the five knobs now do anything, but that clunker still has to go. Anything close is better than what's on there.....:thmbsp:

[bricktop]

If I were you, I'd strip out all the tone control, selectors, etc and just make them pure monoblocks (unless you do use the phono sections of course, or want to keep them original). Then you can slap some nice wood trim around and not have to worry about knobs, rusty panels, lettering, etc. :thmbsp: