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I started my Tramp build a year ago only to be temporarily relocated and had leave it behind. I regularly read this forum while I was gone and looked forward to the day I would be able to finish the build. Well I'm back home and finished the amp (the cosmetic cabinet finishing is next). Unfortunately everything checked out fine with no tubes/load but after putting the tubes in most of readings were 30 VDC low (line voltage is through a step down transformer as I am in Hong Kong and is 110 VAC. There is no noise at all and the amp seems too quiet and stays clean when dimed out. The VRM seems to be working but with it at 100% (everything else at minimum the voltage is 373 the rest in order are 26.38, 310, 171.5, 169.3, 1.57, 1.5. Because time had passed, I downloaded the latest revision of the drawings to finish the amp. I thought it may have been an issue with the caps being reversed but they appear OK. Can anyone lead me in the right direction. I have triple checked everything and looked for cold solder joints.

Welcome to the forum.

Looking at the picture of your amp wiring, I did not see if the 22 K resistor of the volume pot is connected to the 8 ohm tap of the impedance switch.

Usually this connection is easy to see because it crosses over the component board. Maybe you routed it under the board?

I don't know what effect this connection would have if missing.

Nice looking build first off.

You need 120V AC for your input. 110V is too low, the amp wa designed for 120V.

With single coils the amp should stay clean with all the controls dimed.

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Thanks Gotie - I indeed ran the wire from the impedence switch to the volume pot under the board
Kurtlives - Thanks I thought that the low line voltage might have something to do with it. Will it hurt any thing to operate it this way until I can find a variac or a transformer that will take Hong Kong's 220 VAC down to 120 VAC?

Your heater voltage shouldn't go more than 10% above or below 6.3V, or the power tubes will suffer reduced life time. So first measure your heater voltage.

There is a trick I just posted on PPwatt.com a few minutes go for someone asking the same kind of question. Get yourself a cheap mains transformer that puts out around 9VAC say, which some solid state circuits use. Wire the secondary of that transformer in series with the primary of your amp's PT and the mains AC supply. Provided you apply the 18V AC in phase with the mains AC coming into the PT primary, it will add the 9V or so to the AC voltage seen at the PT primary, and you will get the correct voltage appearing at the PT secondary windings. If you find you get a voltage drop instead, just swap the secondary connections of the low voltage auxiliary transformer, to get the phase right. The you will find your PT producing the correct secondary voltages.

Effectively, it's a Vintage Voltage Adaptor phased to boost rather than reduce voltage - http://www.geofex.com/Article_Folders/v ... ntvolt.htm

HTH

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Great tones come in small glass jars!

Can you get a 120V step down. You're really only 10/120 or off 8% off. What is the amp like in tube/fat mode?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Zaphod - Thank you for the great tip. I work in the electrical generation business and I talked to a few of our "experts" about the situation and not one suggested anything close to your solution.

Stephen - One benefit of being in Hong Kong/China you can usually find anything, including a wide array of transformers at reasonable prices. Quality is another story. The trick is finding them. I need to travel to the States for holiday today but upon return I will first try to find a suitable transformer (I might even be able to get on made - if I can find someone who speaks English). If not successful, I'll try Zaphod's suggestion. I deffinately need to resolve this problem because I have a TC-15 to build next. Thanks for the help.

I returned from holiday and found a 220/117 VAC transformer (I could not find a 220/120 but I though this would be close enough). There was a slight improvement in volume but still too clean when dimed. In the process I noticed that the volume pot and the tude/tweed were having no effect. While checking everything again I noticed a discrepancy between the posted schematic and the layout I used - the schematic shows pin 1 of the preamp tube connected to C2; on the layout currently posted pin 6 is connected to C2. After going back to the original layout sent with the kit (which I did not use), it does match the schematic. Am I seeing things correctly and if so, which is correct? Any help would be appreciated.

Can't really see by your pic but try swapping the wires on pins 1 and 6.

The layout in the Resource section is currently wrong. It needs those two pins switched.

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Thanks Kurtlives - I swapped the leads on pins 1 and 6. Everything now appears to be working. After checking the dc voltages against the layout, with a line voltage of 116, I got 392.4, 28.16, 325.3, 168.6, 181.5, 1.7.2 and 1.7. Although there is some deviation at R4 and R9, it is still less than 5%. Considering the line voltage difference of more than 3%, is it safe to assume that these readings are ok? In addition, with everything dimed out, there is now noticeable hiss but it seems less than my other amps, with the possible exception of the AC4TV. I assume this is normal for a Tramp? I want to thank everyone for your kind assistance. It is early in the morning here in Hong Kong but I can not wait to give the Tramp a ride and wake up the neighbors.

Those voltages look good! Once you get 120V AC in they will be even closer, doubt you'll notice any changes to the tone though.

Hiss is normal at high volumes. Abnormal amounts of hiss or hum is bad.

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Thanks again Kurtlives! Played with a Strat, the 6V6 and a TT Alnico and to me it sounds great. Going to be trying a 6L6 and EL34 next which is easy now that I used you impedance switch wiring suggestion.

One last question, I have some JAN 6L6WGB (Philips) on hand for a while. Is there any issue using these in the Tramp or should go out and buy new 6l6GC which I think I read is what is required for the Tramp?

Now to finish the cabinet cosmetics and then I,ll be trying my hand with the TC-15.

I asked Zaphod about the 6L6WGB tube in the Tramp Tubes thread. They won't take the dissipation and will red plate...not good.

Jim

Jim - thanks for checking. It is appreciated. Too bad though. I went to HK's main music store, Tom Lee and they are going to have to order some 6L6GC for me. All they carry are the 5881 type 6L6.

Really? That surprises me, as true 5881s are only available as NOS and for big $$. So are those particular tubes "Sovtek 5881"s by any chance? If they are, then they're not really 5881s at all, but actually a tube used in Russian bombers that's even more rugged than a 6L6GC. We used one of those "Sovtek 5881" tubes when developing the Tramp and it was even gigged with that tube inside.

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Great tones come in small glass jars!

Zaphod - the seemingly very knowledgeable guy at Tom Lee said the Groove Tubes GT 6L6-R (the only 6L6 they carried) were Russian made and were not 6L6 GCs.

Not being knowledgeable myself I took his word for it and asked them to order me some GLG GCs for use in my Tramp. I have since checked the Groove Tube site and for the GT-6L6-R (B) they had this description “Russian made, same as the 5881 you are using now, but when these are matched in our system they are improved. These are a very sturdy and reliable tube.”

On Amazon, this is part of the description, “GT-6L6-R (B) Duet Russian made, same as the 5881, ... These are the tubes that are used by Fender in amps that use 6L6 tubes and are amps that DO NOT come from their custom shop.”

I did not see Sovtek on the tube though. Do you think these tubes might indeed work in the Tramp?

I wouldn't rust anything that GT's marketing BS department says. GT basically bulk buys anything they can get cheap, the tests and re-labels them so they can charge a premium price. I have a hunch they may actually be selling the same heavy-duty military tube here that Sovtek is falsely relabelling as a "5881". Are there any pictures of this tube? If it has a thin black base (aka wafer base), then it probably is the same tube, which *isn't* a 5881.

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Great tones come in small glass jars!

Zaphod - the next time I'm in Tom Lee, I'll try to get a photo of the tube in question.

The plastic base of one of those Russian "not-5881"s is very distinct, because it's just a thin wafer of black plastic. Other distinguishing features are the flattish top of the tube and the oval slots in the anode.

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Great tones come in small glass jars!

Zaphod - The 6L6s at Tom Lee were not what you were describing. I was able to find a couple of Tung Sol 6L6GC-STRs here in Hong Kong. I finally finished covering the amp in leather. It was definitely a learning experience. I will have to think about it twice before I try it again. I want to thank everyone for their help. I may need more when I start building the TC15 kit that is already calling my name. I can not say enough about the quality of the Tramp kit and the outstanding tones it produces.