1972 Traynor YGL3A

[mondo]

Hey Folks,
I pulled the lid off my Mark III Traynor head to have a peek at what was modded. I bought it in this condition and I really like the sounds I'm getting from it. This amp is basically a beefy 100watt EL34 version of a Twin with Tremelo and Reverb circuits in the effects channel. It also has an original master volume that has been rewired. The straight channel(without effects) was overhauled with extra gain stages and what sounds like a marshally tonestack. The straight channel is really gainy and british sounding but brighter and unique which is why I like it. The reverb has been disconnected and the reverb jack is my footswitch jack. The second jack input on the effects channel is plugged off and I was told not to use it by the guy I bought it from. What I'm wondering is why the guy would have left in the original mallory 40/40 filter caps? These things are 40 years old and my amateur opinion would lead me to think that the first order of business would be to do a re-cap on it before tinkering elsewhere. On further examination I notice that the primary (red) lead on the output tranny is browned nicely and the light brown rectangular cement resistor(thyrector?) connected to the primary has been so hot that it burned the paper on the eyelet board. There is some solder melted to the side of this brick too! This amp apparently has 2 thyrectors in the output stage to protect it from open loads. This may be an old problem that was fixed but I am scared to run it now that I can see these old mustard caps. The amp is SILENT. No hum. Any input will be graciously received and faithfully applied.
Cheers

[mondo]

Here is a pic of the problem. You can see the red lead from the primary winding of the OT turning brown. It connects to the two big rectangular brown things which look like power resistors. Anyone know what a thyrector looks like???

[mondo]

Here is the rest of the circuit.

[mondo]

And a schematic.

[Jazz P Bass]

If the filter caps do NOT let undue ripple through to the B+, then they are still "good".
Seeing that the amp is silent bolsters that thought.
The Vac ripple can be measured with a DVM.
Yeah for peace of mind you could replace them.
Then again you may not like how stiff the amp gets.
As to the thyrector , test them as you would a diode.
The schematic that I have indicates a 1N5062 diode.
Not a thyrector.
I guess they changed them.
The red wire turning brown could be a sign of age.
Or abuse.
I have replaced a number of failed Mark3 output transformers.
They seem a bit small for the output wattage of the amp.

[1ampman]

I've been using that amp for the past 11yrs for rehearals and gigs. It's never let me down besides have a wonderful tone. The only mod I did was to put reverb and trem on both channels otherwise it's stock. Including the electrolytics. It's quiet and problem free. I installed Sovtek 5881's when I first got and don't really need 100 watts. I tried many amps and always prefer this. The Mallory's in my amp were made in Canada. I'm NOT looking to change the tone so that's why I keep hanging on to the stock parts. One thing I notice about Traynor amps is the opto trem roach on most are crap. With a few resistors changes the Fender roach works excellent. I feel these old Traynors are built more rugged and better than any other factory built amp. Yes, this is a beast to carry and people ask me why. Well, for me and my situation, it's the best! Oh ya, it's ugly !!!

[g1]

"light brown rectangular cement resistor" - that's what they are, the 470R 10W resistors R23 and R43. The thyrectors are probably long gone as when they failed you could just remove them or put in diodes for protection. The board and wires probably got charred when one of those power resistors fried, the solder is probably from that repair. Is there supposed to be some kind of problem with those "mustard caps"? As far as I know they don't have age issues like electrolytics do.

Some interesting things about the circuit if anyone would care to comment:
1) There is a common screen resistor (470R10W) then smaller ones on only 2 of the power tubes, why not on all?
2) Am I correct the 120ma total bias current called for would be a fairly cold 13W per tube?
3) Using the common screen resistor to measure bias (8 volts across 470R = 120mA total plate current) may have worked in 1972 with tight tolerance 6CA7's but would not be very accurate with modern tubes?

[mondo]

Well that's good news! Thanks for everyone's input. This is the first circuit I have ever spent any time trying to figure out so I am admittedly a noob when it comes to working on amps. The concern I had with the Mallory filter caps was mostly because I have been watching some Youtube tutorials over the past few months posted by Pat Furlan. He does a lot of work on old Traynors and in some of his videos he seems to like replacing these old "mustard" caps with somewhat equivalent Marshall FCaps. A lot of folks seem to think this is an essential part of the maintenance on older tube amps and that the consequences of running current through old caps can be very pricey. Does anyone seem to think there is an undue risk in leaving these old firecrackers be? I can test them every few months if that's all that is required. As far as the nicely toasted lead and resistor on the OT and eyelet board, it looks like that was fixed because there is unburned tape and fresh green wire underneath.
I have had a lot of nice amps over the years but this one is special to me. I just recorded 8 new songs and everyone involved seems to agree that this old warhorse is the nuts.

[Gtr_tech]

[ATTACH=CONFIG]14632[/ATTACH]

Here is a pic of the problem. You can see the red lead from the primary winding of the OT turning brown. It connects to the two big rectangular brown things which look like power resistors. Anyone know what a thyrector looks like???

That brown thing with the yellow dots is one of the spike protection device. I don't see the other one, but if its still in there it will be tied to the plate of one of the output tubes. I don't trust them and always remove 'em.

[g1]

I think you are calling the main 40/40 filter cap a mustard cap., thus my confusion. The smaller round mustard coloured coupling caps on the board are mustard caps.
As far as the main filter cap goes, generally when these type fail they just go open which will cause more hum but not damage anything.
It is hard to see in the pics if that spike suppressor (dark brown with yellow dots) is still really connected, but like Gtr_tech said, best to just remove it from the circuit.

[mondo]

The schematic in the lid says TH1 and Th2 which I presume are these thyrector diodes. The Traynor website says that the older models had a thyrector (singular) in the output stage. My amp has one of these tied to the OT and plates of the effects channel's power tubes. I can see that one on the left connecting to the straight channel's plates was clipped off already. What happens if I remove the other one?

[mondo]

"I think you are calling the main 40/40 filter cap a mustard cap., thus my confusion."


AHH! Thanks for correcting me G-one! Is the spike supressor you refer to also known as a thyrector? It is connected where the thyrector is on the schem but the other one was snipped out of the straight channel. Having never seen a thyrector I was confused because I was looking for two of them. Apparently when they blow they smell like rotten eggs and make a mess. Would it be worthwhile to insert an equivalent diode there to replace it?

[Gtr_tech]

Its a mono pwr amp man....there is no "effect channel power tubes". Both channels use a common output section...

[Jazz P Bass]

Look at the schematic that I posted above.
They used (2) 1N5062 diodes in series to ground on each side of the output transformer.
Correct polarity must be observed.

[g1]

Yes the thyrector is a spike suppressor. However it is selenium rectifiers that make the rotten egg smell & mess and you will only find them in stuff that is even older. You can clip it out and if you like replace it with the diodes as JazzP suggested, see the other schematic in the manual he posted if you want to do this.
As Gtr_tech noted, this is a mono power amp, all four power tubes are working together. You have two preamp channels but both go through the same power amp.