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Anybody Reccomend a Tube Amp Geek Site?

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Hyperborea
(@hyperborea)
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Joined: 16 years ago
Posts: 827
Topic starter  

I've picked up for a great price a somewhat older tube amp from the 70's that hasn't seen much use that's in great condition. It's a 1977 Traynor YGM-3 GuitarMate. It's a 25 watt point-to-point el-84 tube amp with spring reverb and a tremolo (both tube driven!). It's got a sound of it's own but if you have to compare it's something like a mix of a Fender Deluxe Reverb and an early Marshall. Great sound for the blues and classic rock.

Now, the problem. It's in great condition because it hasn't seen much use and was a bedroom amp all of it's life. In fact it's been in storage for the last 5 years or so (the previous owner got kids and went acoustic). That means that the electrolytic capacitors are dead (at least some of them). You can hear that when you use the amp (muddy, too bassy, loss of volume, static). I'm pretty handy with a soldering iron, I understand electronics and have hands-on experience (though before this everything has been digital or low power analog and hands on was a while ago), I understand the theory of tube amp operation, but I have no practical experience with tube amp repair. (all of the preceeding was to avoid the "don't do it", "it's too dangerous", etc. comments)

Does anybody have any recommended tube amp geek web-boards to go to for advice? I'm having trouble finding some equivalent replacement caps and looking for advice on selecting replacements. Should all of the caps be replaced or just the big power filter caps? How about the small pre-amp tube bias caps (they are electrolytic)? Anything else that should be done or replaced other than a general cleaning (contact cleaner in the pots, etc.)?

Thanks

Pop music is about stealing pocket money from children. - Ian Anderson


   
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DemoEtc
(@demoetc)
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Joined: 20 years ago
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There's a few people here who are tube amp geek sites all by themselves - Ricochet among them ;)


   
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Hyperborea
(@hyperborea)
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Joined: 16 years ago
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Topic starter  

There's a few people here who are tube amp geek sites all by themselves - Ricochet among them ;)

Sure, if anybody here has any advice on servicing the amp that would also be appreciated. I asked about a "tube geek board" because I haven't seen too much hard core geek postings here.

Pop music is about stealing pocket money from children. - Ian Anderson


   
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Moonrider
(@moonrider)
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Joined: 18 years ago
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http://www.thefenderforum.com/

Register for the forum, hit the Amplifier section and do a search on the topic, post leftover questions. There's a couple of people there that build their own amps and can give you some very solid advice

Playing guitar and never playing for others is like studying medicine and never working in a clinic.

Moondawgs on Reverbnation


   
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racetruck1
(@racetruck1)
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Joined: 17 years ago
Posts: 518
 

OMG, another Traynor convert!

And another fan of Robert E Howard!

A really great site is "Velvet Black", pretty much all Traynors and their history, lots of schematics also.

When I get a chance to look at the schematic on my other computer, I might be able to see what will work, there is some leeway on the caps.

Google "tube amp schematics" and you will find everything from beginner sites to hardcore "Geek" sites, I have a bunch but I can't get to them just yet, I got a new computer and I haven't sorted it out yet. When I do, I'll E-mail them or PM them.

When I die, I want to go peacefully in my sleep like my grandfather, not screaming......
like the passengers in his car.


   
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TimeZone
(@timezone)
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Joined: 18 years ago
Posts: 205
 

You'll find a few of us here who are quite willing to geek it out with you. I think everyone else ignores us when we get into geek mode. ;)

Linkies:
Ted Weber mostly sells speakers, amp kits, and parts. Also has a bulletin board, mostly for his own kits, but a lot of people there are friendly and if you go in the "technical" section or "amp kits from other companies", they'd probably help you.
The Gear Page also has an "Amp Technical Info" section.
The Vintage Amps Bulletin Board is decent, though they don't have a section dedicated to Traynors. Try the "Miscellanious American Amplifiers" forum, probably close enough.
Tube Depot is another good source of parts.

As to your specific questions, basically anything that's an electrolytic probably needs to be replaced. I went through this a couple months ago with a Gibson GA-5 I picked up to refurbish. (thread here.) I tried to replace as little as possible, but in the end, every electrolytic needed to be replaced. So that would include your cathode bypass caps (preamp as well as power). (I did need to replace those on mine, they were basically shorting, so the pre-amps had no bias, and therefore no volume.) Other than that, the resistors may have drifted. I did not have any huge problems with the resistors. Some of them were off, but overall, my voltages were in the right ballpark, so I did not bother replacing any of them. I say start with the electrolytics, and see how it goes. If you're ordering parts, it may make sense to just order the resistors anyways. If you don't need them, it's only a few dollars that you wasted. If you do need them, you'll be glad you don't have to put a second order in.

I'm sure Ric will chime in at some point too. I'm trying to learn, but he knows a whole lot more than I do. :)

A mix of a Deluxe Reverb and an early Marshall, eh? Time to go research Traynor amps.... ;)

TZ


   
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Ricochet
(@ricochet)
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Joined: 19 years ago
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Here's one I like: http://music-electronics-forum.com/ There are a bunch of experienced amp builders and techs who hang out on there who can tell you how something will work.

The home amp building sites, like http://ax84.com/ are useful resources for amp repairers and tinkerers as well.

The tube amp pages linked off of http://www.geofex.com/ are quite useful.

"A cheerful heart is good medicine."


   
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Wes Inman
(@wes-inman)
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Joined: 19 years ago
Posts: 5582
 

Amptone is a great site with tons of useful info.

http://www.amptone.com/

If you know something better than Rock and Roll, I'd like to hear it - Jerry Lee Lewis


   
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Hyperborea
(@hyperborea)
Prominent Member
Joined: 16 years ago
Posts: 827
Topic starter  

OMG, another Traynor convert!

And another fan of Robert E Howard!
Yup, I read a lot of Howard's books as a kid. The name "Hyperborea" is also from Greek myth and means "beyond the north wind". As a Canuck the name seems appropriate (though I currently live in the SF Bay Area). Perhaps another factor in my becoming a Traynor convert (good Canadian amps from "Tranna" - Toronto).
A really great site is "Velvet Black", pretty much all Traynors and their history, lots of schematics also.
I really liked that site and used it for info when I was considering buying the amp.
The Vintage Amps Bulletin Board is decent, though they don't have a section dedicated to Traynors. Try the "Miscellanious American Amplifiers" forum, probably close enough.
Actually, I read a lot from this site and that particular board before buying the amp. There are a lot of good threads discussing Traynor amps there. I've been trying for a while to get authorized to post there (maybe 5-6 weeks - I tried before my vacation and again after). You need the site admin to approve you and it didn't happen after I used the sign up procedure so I tried emailing them directly and still no success. If anybody has an account on this board could you email the admin and ask them to approve my account? It's the same name as my account on this board - "Hyperborea".
You'll find a few of us here who are quite willing to geek it out with you.
Well, a couple of questions then.

1) Choosing replacement caps. I think I need to keep the voltage the same or greater and the capacitance in many cases should be similar though going up to maybe 50% over would be ok if the exact value can't be found. Correct? High heat models or normal? What about sizing considerations? If the new cap won't fit between the two resistors on the board like the old does can the new one "ride" on top of them?

2) Mounting cap cans. Mine is the later version YGM-3 (black and silver bumpers) and the two cap cans are mounted internally using straps to the chassis and not hanging down like the tubes do (earlier YGM-3 models did this). Those cans are pretty close to 1" in diameter but all the replacement cap cans seem to be 1 3/8". I don't think I can stretch / open the existing clamps enough to fit the new cans. Any suggestions for mounting them?

3) One of the caps on mine seems kind of oddly numbered. I can't read all of the component numbering without taking it out but it appears to read "015". From the schematic for the amp ( http://www.informatik.uni-bremen.de/~dace/vb/traynor_guitarmate_ygm3a.pdf ) this is C20 and should be 5uF. What should I use here? It is the original cap so it's not some later mod.

Thanks to everyone who replied - all good advice.

<edit> The board software turned my Greek micro symbol into a question so I replaced it with a "u".

Pop music is about stealing pocket money from children. - Ian Anderson


   
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TimeZone
(@timezone)
Estimable Member
Joined: 18 years ago
Posts: 205
 

1) Choosing replacement caps. I think I need to keep the voltage the same or greater and the capacitance in many cases should be similar though going up to maybe 50% over would be ok if the exact value can't be found. Correct? High heat models or normal? What about sizing considerations? If the new cap won't fit between the two resistors on the board like the old does can the new one "ride" on top of them?
Definitely keep the voltage same or greater. For the power filter caps, it probably wouldn't hurt if you used somewhat higher capacitance values, but do be aware that it will change the response of the amp. (Also, I don't understand the specifics, but I seem to remember reading something about tube rectifiers not being happy if you use too high of a filter cap value. Not sure if your amp is solid state rectified or tube rectivied.) I'd stick as close as possible to the original values. Don't sweat things like 48uF when all you can find is a 50uF, but I wouldn't go willy-nilly changing 50uF to 100uF. For signal caps (and this includes the cathode bypass caps), I would not change cap values unless you are attempting to achieve something specific. For sizing, modern caps are generally smaller than the old ones, so you probably won't have any problems.
2) Mounting cap cans. Mine is the later version YGM-3 (black and silver bumpers) and the two cap cans are mounted internally using straps to the chassis and not hanging down like the tubes do (earlier YGM-3 models did this). Those cans are pretty close to 1" in diameter but all the replacement cap cans seem to be 1 3/8". I don't think I can stretch / open the existing clamps enough to fit the new cans. Any suggestions for mounting them?
Tube depot sells different sized mounting clamps, although I think they're only for the "hanging down line the tubes" style of mounting. Having a hard time picturing what's in your amp, so I don't know. If you mean that there's a clamp inside and the thing is laying down, clamped down next to the circuit board, then I dunno.... I had something like that in my Gibson, and I ended up replacing the can with two individual caps. I know, I know, it doesn't preserve the vintage look... whatever.
3) One of the caps on mine seems kind of oddly numbered. I can't read all of the component numbering without taking it out but it appears to read "015". From the schematic for the amp ( http://www.informatik.uni-bremen.de/~dace/vb/traynor_guitarmate_ygm3a.pdf ) this is C20 and should be 5uF. What should I use here? It is the original cap so it's not some later mod.
Dunno on this one. I've never really been able to figure out from the strange markings on some caps what the heck they are. Unless it comes right out and says "5uF" (which thankfully, most electrolytics are labelled like this), then I always have to resort to measuring the stupid thing to see what it is.

re the Vintage Amps BB. Sorry to point you to a board where you can't join, that sucks! I don't have an account there, I only pop by and read / research stuff every now and then. Hopefully you can find someone to put a good word in. Have you tried writing from a different email address? spam filtering software is sometimes too aggressive...

TZ


   
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Ricochet
(@ricochet)
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Joined: 19 years ago
Posts: 7833
 

Definitely keep the voltage same or greater. For the power filter caps, it probably wouldn't hurt if you used somewhat higher capacitance values, but do be aware that it will change the response of the amp. (Also, I don't understand the specifics, but I seem to remember reading something about tube rectifiers not being happy if you use too high of a filter cap value. Not sure if your amp is solid state rectified or tube rectified.) I'd stick as close as possible to the original values. Don't sweat things like 48uF when all you can find is a 50uF, but I wouldn't go willy-nilly changing 50uF to 100uF.
This is really a more important issue than generally realized. The peak cathode current of a rectifier tube with a capacitor input filter is determined by the size of the capacitor in the first node of the filter, and the maximum values are rather small. For a 5U4GB, you generally can't go past about 50uF, and with a 5Y3GT, 10uF or so, without exceeding the allowable peak cathode current pulse limits and shortening the life of the tube. (It'll probably work fine for a while, but the tube's overstressed.) You can get around that by inserting series resistance between the rectifier tube cathode and filter cap, and that's actually a good idea. It avoids the high inrush current when the capacitor is first charged up and lets you use a larger filter cap than you can use safely with a given rectifier without the resistance. (It's actually good practice to use some series resistance even with solid state rectifiers.)

Like the sound of rectifier sag in a Class AB amp? Use smaller filter caps and higher series resistance. That works if you've got a solid state rectifier, too. (Won't make any difference if you're running in true Class A conditions. No sag there.)

These are general comments. I haven't got a clue what's inside this particular Traynor amp, which is why I've been basically staying out of the discussion so far.

:D

"A cheerful heart is good medicine."


   
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Ricochet
(@ricochet)
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Joined: 19 years ago
Posts: 7833
 

I was just pulling those capacitance numbers out of my head from what I typically use. Just opened up the RCA Receiving Tube Manual RC 30 to see what they said for the 5U4GB for input filter cap ratings for typical operation: 40uF. 50's probably pushing it and should probably be regarded as a working max. Won't hurt to put a few ohms between that cap and the cathode. Rectifier tubes have a tough life.

"A cheerful heart is good medicine."


   
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Hyperborea
(@hyperborea)
Prominent Member
Joined: 16 years ago
Posts: 827
Topic starter  

Ok, no worries on the rectifier since it uses discrete diodes for that and not a tube.

Here are a few pictures of the innards. The first is the amp with the top off (the Traynor has a pretty cool feature for access - if you take out the four screws on top then the top comes off giving access to the board). You can see how clean it is inside.

Here are the closeups of the two cap cans. Any suggestions on putting in the replacement caps which have a bigger diameter than the original and probably won't fit into the straps.

The electrolytic capacitors are all the blue caps.

Other than the cap cans these are listed in the order across the board from left to right as pictured above:

  • C21, C30, C32, C32 - 40uF 450V (in the two cap cans)
    C28 - 8uF 250V
    C29 - 64uF 64V (on the board this is 68uF 63V)
    C25 - 25uF 25V (on the board this is 22uF 25V)
    C20 - 5uF 64V (all I can read is 015)
    C9 - 25uF 25V
    C3 - 25uF 25V
  • What I can find as replacement caps using Vishay/Sprague or similar (Mallory appears to be out of the electrolytic cap business) trying not go below the original voltage nor below the original capacitance:

  • 2x40uF 450V (cap can) ===> 2x50uF 450V (cap can)
    8uF 250V ===> 8uF 450V
    64uF 64V ===> 100uF 100V
    25uF 25V ===> 25uF 25V
    5uF 64V ===> 8uF 150V
  • Are these ok replacements? Any suggested changes?

    The only big jump is for C29 which goes from 64uF to 100uF but this is part of the output tube bias circuitry so that should be ok, I think. It will just mean that it takes a fractional second longer for that to charge up. It's kind of messy in that part of the circuit since the tremolo works by "wiggling" the bias voltage on the output tubes (interesting idea). Will that cause a problem with the change in value of C29?

    Thanks

    Pop music is about stealing pocket money from children. - Ian Anderson


       
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    Ricochet
    (@ricochet)
    Illustrious Member
    Joined: 19 years ago
    Posts: 7833
     

    I doubt you'll have a problem with C29. If it does change anything, it'll slow down your tremolo a little. To find out, get a cap of appropriate voltage and 40-50uF, and clip it in parallel with C29 and play.

    Everything else is OK for sure.

    "A cheerful heart is good medicine."


       
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    racetruck1
    (@racetruck1)
    Honorable Member
    Joined: 17 years ago
    Posts: 518
     

    Lotsa room inside for a bigger cap, I make larger straps from thin aluminum stock like what is used in soffit and fascia in a house. If you know a general contractor or siding mechanic, they can give you a small strip. The nice thing is that you can cut it with a good stout pair of scissors or score it with a razor knife and straight edge and bend and snap.

    You can also relocate them in an area with more room and extend the wires, I think as long as they are in the same metal enclosed area.

    I'm not sure if they have to be shielded, but I noticed that on Fender amps, they are mounted on the same surface as the tubes and are covered with a metal pan. I would guess to shield the wires, and as a safety issue in case they blow. The actual caps themselves are already in metal cans but the ends are not.

    Another way is to use "surface mount" can caps but that would mean cutting holes in the chassis, maybe a little more effort than you want to do.

    These would stand upright and have two ears on them so you can bolt or rivet them on the chassis with the wires going into the amp chassis.

    BTW, ther should have been a schematic for this amp on the "Lid" of the amp, glued to the piece of sheet metal stapled to it. At least that is where mine is in my Mark III, which looks almost exactly like yours, right down to the "bumper car" trim!

    When I die, I want to go peacefully in my sleep like my grandfather, not screaming......
    like the passengers in his car.


       
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