Well, what should I do with the T1RVT

capnjuan

Gone But Not Forgotten
Gone But Not Forgotten
Joined
Nov 29, 2006
Messages
12,952
Reaction score
4
Location
FL
zulu said:
capacitors, soldering tool ordered. $16.95. Telling Mrs. Zulu I made a music related puchase for under $20.00.....priceless.
Well ... you're okay for now ... the problem comes when you get either bogged down or really interested in bench work ... and spending time there by yourself ... she's going to think you don't appreciate her company ... or you think she has BO ... you may be stuck watching a lot of TV you don't like as proof of your affection ... comes with the hobby. :wink:
 

zulu

Senior Member
Joined
Dec 14, 2008
Messages
2,132
Reaction score
1,801
Location
NV west of Los Angeles
Guild Total
4
:)

I found another capacitor I'd like to change. It's the one on the speaker feed to the reverb. cap (and schem.) show a 5uf-64v. Would it be ok to put one of those 25uf-25v Spragues in there?
 

capnjuan

Gone But Not Forgotten
Gone But Not Forgotten
Joined
Nov 29, 2006
Messages
12,952
Reaction score
4
Location
FL
zulu said:
... I found another capacitor I'd like to change. It's the one on the speaker feed to the reverb. cap (and schem.) show a 5uf-64v. Would it be ok to put one of those 25uf-25v Spragues in there?
Hi Z: ... I can't go for that, oh-oh, no can do .. A member threaded the evolution of Guild reverb Here. Said to work well in good-running amps; in retrospect, speaker-driven reverb has to be seen as something of an experiment ... eh ... therefore necessarily sensitive.

Other than Guild and Sano (must be something in the NJ water), no other mfrs fooled with speaker-driven reverb. I'd like to offer a technical explanation of the specified values but I don't have one. I will say that you'd be reducing the voltage handling by 50% (injecting a safety issue where there wasn't one before) and increasing uf by a factor of 5 and it's not nice to fool Mother Nature.

In Spanish, the expression would be: 'Let that dog that sleeps lie'.

Whatever you put in, be sure to observe polarity. John
 

zulu

Senior Member
Joined
Dec 14, 2008
Messages
2,132
Reaction score
1,801
Location
NV west of Los Angeles
Guild Total
4
Thanks cap. Good lesson on the reverb, too. I'm getting a little better understanding everyday. Last night I looked up the schematic for my Ampeg B 25, which is a simpler circuit, and I could follow the signal flow, and ID the power supply, rectifier, preamp sections, etc. Then I went back to the T1RVT, and it's making more sense, too. I still don't understand most of the theory, (like what a rectifier is actually doing and why), But I can "see the schematic in the chassis" so to speak.

It's also bringing back memories of my terriffic high school electronics teacher, Mr Guske, who was the definition of a nerd (maybe why we got along so well :? )... I digress

About that 5uf-64v cap. I see what you're saying. Maybe I'll leave it in there, because the reverb is working well, but it's got the ooze going on.

What about something like this:
http://www.tedss.com/item.asp?id=2020002304
 

capnjuan

Gone But Not Forgotten
Gone But Not Forgotten
Joined
Nov 29, 2006
Messages
12,952
Reaction score
4
Location
FL
Hi Z; Ooze? Needs to go - that one is too much $, use this one: 8uf/150V
 

zulu

Senior Member
Joined
Dec 14, 2008
Messages
2,132
Reaction score
1,801
Location
NV west of Los Angeles
Guild Total
4
Ok. Operation complete. It was fun. I have successfully brought myself back to square one. :lol:

Due to the relative anonymity of this forum, I'm willing to post a pic of my work, yes it's ugly as heck, but I didn't burn myself or install any damage to the amp in the process (that I know of). I feel reasonably sure the new components are installed with the correct polarity and continuous, albeit amateur, solder joints.
DSCF2231.jpg


The amp powered up, ran well for 15-20 minutes, then the old fade to black.

more in a moment..
 

zulu

Senior Member
Joined
Dec 14, 2008
Messages
2,132
Reaction score
1,801
Location
NV west of Los Angeles
Guild Total
4
A couple of things:

I have to consider every tube in there right now untested. even the preamp tube I had in there last week is back in the twin, and a bought a "new" GT 12ax7m for the Guild. Maybe I'll swap those 12ax7 tubes because that china in there worked longer last week. I also managed to knock both power tubes out of their sockets re assebling, and had to bend the pins back straight. :roll: I'll start looking for a local with a tube tester.

The capacitor that feeds the reverb tank
Hi Z; Ooze? Needs to go - that one is too much $, use this one: 8uf/150V
has not been changed. I put the oozing one back in for now, anticipating adding to the parts order.
--speaking of the reverb, while it was running for a short time last night after re-assembly, I think I was getting less reverb signal than previously. I needed to turn the 'verb up halfway before I could really hear it, it used to be pretty wet at halfway.

The can caps: both of these exact can caps are available, but I'm hesitating to order not knowing how old these are for sure. I mean, if the four digit code on them is a date code, they're both 07XX. when I bought the amp in 08, it had "recent service". John, you said you think they might be original, do you think I should get new ones just for good measure?

Next steps after work tonight: 1. I think I'll put that other preamp tube back in, FWIW amp has worked best with that tube, probably coincidence.

2. then I'll go thru the voltage checks outlined earlier in the thread.
3. Thinking about just adding "thanks capnjuan" to my sig line.
 

capnjuan

Gone But Not Forgotten
Gone But Not Forgotten
Joined
Nov 29, 2006
Messages
12,952
Reaction score
4
Location
FL
zulu said:
John, you said you think they might be original, do you think I should get new ones just for good measure?

Wait for the results of the voltage checking; you need to leave the amp on until it dies and then do the voltage checks. If after the amp dies out and you have no/low voltage at any of the hot posts, then we'll talk about it. You can turn the amp on and leave it on your bench for the 20-30 mins provided you pull the output tubes out.

1. I think I'll put that other preamp tube back in, FWIW amp has worked best with that tube, probably coincidence. OK
2. then I'll go thru the voltage checks outlined earlier in the thread. OK
3. Thinking about just adding "thanks capnjuan" to my sig line. Thank you; I'm (nearly) always happy to help. :wink:
I wouldn't worry too much about the 6GW8s ... they're tougher than they look. The power supply to the reverb amp is tapped off the primary can cap. The cans look new but also no scratches, solder splatter, and the dropping resistors look original; that is, they don't show any signs of recent work. Also the rest of your amp is pretty clean .... the can caps could still be the original caps but just look as well-preserved as everything else. Can't answer for the date code; any chance of asking the seller what he knows?
 

zulu

Senior Member
Joined
Dec 14, 2008
Messages
2,132
Reaction score
1,801
Location
NV west of Los Angeles
Guild Total
4
. You can turn the amp on and leave it on your bench for the 20-30 mins provided you pull the output tubes out.

Thanks John.

1. run the amp until it dies out
2. pull both output tubes, disconnect speakers and reverb can.<- Is this all done with power staying plugged in and amp power switch on?
3. bench and proceed with voltage checks.
 

capnjuan

Gone But Not Forgotten
Gone But Not Forgotten
Joined
Nov 29, 2006
Messages
12,952
Reaction score
4
Location
FL
zulu said:
. You can turn the amp on and leave it on your bench for the 20-30 mins provided you pull the output tubes out.
1. run the amp until it dies out
2. pull both output tubes, disconnect speakers and reverb can.<- Is this all done with power staying plugged in and amp power switch on?

Below.

If you pull the output tubes while the amp is on - need gloves or oven mitts or something - you do not have to disconnect the the main speaker or the reverb speaker ... in fact, it's better that they stay connected (note below)

3. bench and proceed with voltage checks. Below.

Speakers: the voice coils are the resistive load seen by the output transformer secondary and the output tubes. If the output tubes are in their sockets and the power is on, there is current running through the output transformer that is inducing current on the secondary side. If so, there has to be a load of some kind on the transformer; can either be speaker or a 'dummy load' ... an 8 ohm / 25 watt resistor that is connected to the + and - speaker wires. Can't run the amp without a load of some kind on the transformers.

Bench testing: if you can, this would go better if you could pull the chassis out of cabinet, support it at both ends caps/resistors/component side up, all tubes in, speakers and reverb can connected, and let it run / you can play with it for 20-30 mins until it quits. What we're trying to avoid is turning the amp off and then back on to do the voltage testing. If something is intermittent typically due to heat, then for testing you want the same conditions .... except that after it stops working, you have carefully reached under and dropped the 6GW8s out while the amp is still on.

This won't short or screw anything up ... it's the same as switching the circuit open; there will still be voltages ... make that potentially lethal voltages ... everywhere in the amp but there will be no DC flowing through the output transformers. We're trying to rule out the power distribution and filter capacitors in particular but amp must be in its on - but no workee - condition when you check voltages.

And Zac, it's easy for me to sit here and type this out like it was a recipe for fruitcake but if you have a heart defect of some kind and take 350 volts of dc up your arm, it can stop your heart. Of course, if you're like all the tough guys here, you just get up and brush yourself off and take another hit ... my point is that there are bold amp techs and there are old amp techs but there are no old bold amp techs. With exceptions; this crowd values people using their heads so ... no showing off here. :evil: :wink:
 

zulu

Senior Member
Joined
Dec 14, 2008
Messages
2,132
Reaction score
1,801
Location
NV west of Los Angeles
Guild Total
4
tech help much appreciated, and even more, thanks for caring. although, by the time you're done with me, you might be tempted to outline a 'final' voltage check for me! :shock:

I have taken enough current in my past adventures to make me very cautious. I also work in the aviation business where we adhere to a strict safety culture. That being said, I'm obviously a bit out of my element here, and proceeding with kid gloves. I'll take the time to set up a stable workstation where I can run the amp with the chassis out.


And here's the results of that fruitcake recipe you sent, Thanks!
http://www.youtube.com/watch?v=-UBw-q1wGaE
 

zulu

Senior Member
Joined
Dec 14, 2008
Messages
2,132
Reaction score
1,801
Location
NV west of Los Angeles
Guild Total
4
Ahem.
OK, I set the amp up on the bench with the chassis removed and supported. Everything plugged in (had to make jumpers to reach the reverb speaker). I can do this, man.
Some Alison Kraus playing to further set the mood.
Power switch on, and I'm watching the tubes warm up. Maybe 10 seconds go by, and suddenly I'm plunged into total darkness and silence... Whoah... I feel like Hellen Keller, or am I dead???.......No actually I had a good laugh. Popped the breaker to my room.

Maybe time for me to take a step back and have this baby fixed up right by a tech. I've had my hand in fixing some complicated, precision sh*t through work, and it always comes down to parts is parts and method is art, but, I dunno, I'm ready to start enjoying this amp for more than half an hour at a time.
I'll sleep on it.

Can't answer for the date code; any chance of asking the seller what he knows?
doesn't seem too active around here any more maybe I'll try a pm but, for the record:
I'm still perfectly satisfied with the purchase of this amp. I got a great deal, the amp was just as described, clean with recent service. The issues are just a matter of any vintage item. Hopefully the friendly guy who sold this to me isn't reluctant to chime in If he checks in here anymore.
 

capnjuan

Gone But Not Forgotten
Gone But Not Forgotten
Joined
Nov 29, 2006
Messages
12,952
Reaction score
4
Location
FL
Sorry Zac; I would have replied sooner but I was finishing my fruitcake ... Well ... the good news is that you didn't get zapped ... but I'll bet you an egg-salad sandwich that one of those can sections - new or not - finally shorted itself to ground; blew amp fuse, no? Got any ugliness around the base of the can cap ... or anywhere else; scorching or charring? Sounds like tech time; yours is about as clean as they've come; good luck with it. John
 

zulu

Senior Member
Joined
Dec 14, 2008
Messages
2,132
Reaction score
1,801
Location
NV west of Los Angeles
Guild Total
4
:D
blew amp fuse, no?Actually, no Got any ugliness around the base of the can cap ... or anywhere else Nope, see below; scorching or charring? Nope

No crackling shower of sparks, shooting blue flames, or hovering lightning ball. :(

Didn't blow the fuse in the amp or pop the breaker on the power strip.

The only heat-like damage is that the end of the pilot light, where the leads attach, is a little melty, (been that way, maybe should've mentioned it.)
Thanks Cap, I'll take that bet.
 

coastie99

Enlightened Member
Joined
Jan 1, 2006
Messages
8,662
Reaction score
27
Location
Greymouth, West Coast, Newsyland
zulu said:
:D
blew amp fuse, no?Actually, no Got any ugliness around the base of the can cap ... or anywhere else Nope, see below; scorching or charring? Nope

No crackling shower of sparks, shooting blue flames, or hovering lightning ball. :(

Didn't blow the fuse in the amp or pop the breaker on the power strip.

The only heat-like damage is that the end of the pilot light, where the leads attach, is a little melty, (been that way, maybe should've mentioned it.)
Thanks Cap, I'll take that bet.

Would you like thousand-island dressing on that sandwich Z-man ? :lol: :lol: :lol:
 

capnjuan

Gone But Not Forgotten
Gone But Not Forgotten
Joined
Nov 29, 2006
Messages
12,952
Reaction score
4
Location
FL
Hi Zac: after actually paying some attention to this, it's possible that your 'death cap' - in the red box - finally let go. You don't have to have a polarity switch in your amp to have a line-to-ground capacitor. Since you have a 3-wire cord, that cap has no purpose. You have 2 AC wires inbound and a ground wire. One of the AC wires is tied to the switch and the other to the fuse post ... where that cap is tied. The other end of the cap is tied to ground. It could be internally shorted providing a direct path to chassis ground ... you can check with meter; set to R ... if reads 0 that cap is shorted ... maybe how come the fuse no blow ... or you have a much-to-large amp fuse in there. I see the pre-blow melty condition at the pilot light Sky. That cap, if bad, wouldn't have caused the intermittent condition. If you want, you can snip it out and try again ... keeping your flashlight handy. All that can happen is that you actually blow the fuse or trip the breaker. Also ... the blue circle; confirm that there hasn't been any friction rubbing the insulation off the blue cap; its housing is aluminum and tied to ground; if it's rubbing up against a hot tube socket pin ... I think you see where I'm going.

T1troubleshootZ04.jpg
 

zulu

Senior Member
Joined
Dec 14, 2008
Messages
2,132
Reaction score
1,801
Location
NV west of Los Angeles
Guild Total
4
Would you like thousand-island dressing on that sandwich Z-man
now that sounds delicious, I'll have to try it.

Hey John, thanks for the analysis and suggestions. I'll report back, if able. I'm going to make you a sandwich for your troubles, one for the history books. I've already got one of the eggs.
egg_1372350c.jpg
 
Top