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I have recently noticed the output and fatness of my Tramp has dropped rather dramatically, my Tramp was sounding loud and fat but not now, it seemed to happen mid-rehearsal the other night, output just dropped between songs and the sound became a thin shadow of what it was. This has me a little stumped at the moment and I have checked a few things but can't find the problem. Here's what I've checked so far:

I've measured the following voltages on the 6L6 and VRM at max (VRM appears to be working OK).
B+ at c12 with VRM max = 405 Volts
Cathode Resistors with switch in 6L6 position = 321 Ohms
6L6 Voltages:
Pin 3 = 398 Volts
Pin 4 = 394 Volts
Pin 8 = 27 Volts

Replaced pre and output tube with known good ones
Changed speaker leads
Changed guitar cables
Changed guitars
Changed speaker

I haven't measured the preamp tube voltages so I'll also check those and post back, but I'm beginning to wonder if the OT is the problem here?
I have been running the Tramp with the band and driving it pretty hard both output level (8 - 9) and hitting V1 fairly hard with a boost, the sound was great but it's thin and low output now.

Any other ideas guys?


Snowy

OT don't fail very often while operating during normal conditions. Put that with the over speced over sized Tramp OT and I'd guess your OT is fine.

I'd check preamp voltages first then start looking for cold solder joints.

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http://pdfelectronics.com

Thanks kurtlives. OK I checked the preamp voltages and came up with the following on the 12AX7:

Pin 1 = 190 volts
Pin 3 = 1.72 volts
Pin 6 = 184 volts
Pin 8 = 1.55 volts

Hmmm, I went over the solder points visually, they look very good (photographed most of them for my build thread) and then poked around with a wooden stick, nothing untoward. Very strange, this amp has worked perfectly from startup. I guess I'll have to start re-flowing solder but I see no sign of a problem.

Snowy

Those voltage all look fine. Is this happening in both modes, tweed/tude?

When you turn the amp on now is the sound imediatly low and thin?

When chopsticking don't be afraid to really poke hard at components. I have had pots, impedance switches, resistors with broken lead expose themselves when poked hard with a chopstick that otherwise I would not have seen if poking lightly. Also jiggling wires can expose broken internal leads or issues.

Some pics of the amp right now in it's current state might help.

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http://pdfelectronics.com

OK, I think it's sorted, my Tramp is sounding ballsy again.

I really couldn't find any bad joints, the solder connections on the impedence switch seemed OK physically but they were a Grey frosty colour that I didn't like the look of so I cleaned them up with the solder-sucker and re-soldered them. The two speaker leads I was using to run from the Head to the cab were purchased about 12 months ago from a leading speaker manufacturer that everyone raves about at the same time I bought an Attenuator off them, I hadn't used the leads until I built my Tramp Head, so I took it for granted that they were good. Anyway the plug ends were a bit light-on and cheapish looking so I unscrewed them to check inside and you should have seen the dodgey soldering job, complete with rusted connections and all!! They hadn't even used a insulator around the connectors inside the scew on barrel. Both leads were the same. I got some decent Switchcraft plugs and replaced them.

So I don't know but I'm thinking it was probably the crappy leads. I haven't really played around much with "Tude" mode before since I really liked the "Tweed" setting and just left my Tramp set there but there is a substantial volume jump when switching into "Tude", I take it that is normal. I'll be exploring "Tude" more now.

Thanks again kurtlives for your help and suggestions.

Snowy

Glad you got it working.

Thinking now I have heard people descrebe the symptoms you wire experinenicing thinking it was a blown OT when it was a bad speaker cable.

Tude mode will be louder than Tweed mode, nature of the beast.

_________________
http://pdfelectronics.com

Glad it's sorted. Speaker leads & jacks are a pain point. We once sent an entire replacement amp to a touring musician (just in case) when the service guy went to replace it, said, the solder joint at the speakers were really bad and the cause of the problems. Musician had installed his own speaker!!

As kurtlies said, the Tramp OT is very over spec'd and we would expect it to last a lifetime.

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Stephen
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