'02 Snakeskin Hot Rod Deluxe

[Brad1]

Guy brings a Hot Rod Deluxe to me. Cutting out at higher volumes. No problem, loose solder joint on ribbon cable.

Anyway, measuring voltages, everything as supposed to be, except '96 schematics shows R76 as 1.5K, and to measure -53V. Installed resistor is 82K, and measure -103V.

Did they change that for some reason? The +/- 48V and +/- 16 are right on. All the others OK. No problem?

Thanks,

Brad1

[Chuck H]

It looks the +/- 48V and 16V supplies won't be affected much by that resistor value. How much bias voltage do you have at the tube pins? What is the bias current on the power tubes now?

If your measuring -103 volts where the schem reads -53 it could be that the secondary is a higher voltage than it used to be. That would explain the larger resistor too. If you poke around you may fine other components in this power supply are of different values also. If they're not I would think that C43 is in danger with it's 100V rating.

[Brad1]

How much bias voltage do you have at the tube pins? What is the bias current on the power tubes now?

If your measuring -103 volts where the schem reads -53 it could be that the secondary is a higher voltage than it used to be. That would explain the larger resistor too. If you poke around you may fine other components in this power supply are of different values also. If they're not I would think that C43 is in danger with it's 100V rating.

Thanks, Chuck. I'll have to get back to you on that. Getting ready to leave. I was just wondering if anyone knew for certain right off if they changed some of that for some reason. He said nobody has done anything to it, as far as he knew. It's actually a "Limited Edition" Snakeskin Hot Rod Deluxe.

Have safe and Happy New Year!

Brad1

[Enzo]

The only thing that matters is the bias voltage at the tubes. The Limited Edition just means the decorative finish.

Look at your schematic, are ther a couple caps in the bias supply that don;t seem like they belong? I occasionally find HR Deluxes with the HR DeVille bias supply wired in. They use the same board.

One way, they use a smaller resistor to drop fewer volts, the other way they start with more volts and use a larger resistor to drop more of them. At the tubes, same old voltage.

So not really a worry. But if you wonder, look at the 2001 schematic instead of the old one. it may not match that either, but it will be closer.

[Brad1]

OK...I confused myself. I was getting a bit punchy from spending so much frustrating time repairing broken wires (reverb and ribbon cable) through the day from manipulating that difficult-to-remove board while searching and repairing a couple of cold solder joints. His tubes exhibited some hum and he said they were likely fairly worn, so I popped in a couple of good Mesa-branded 6L6GC tubes (out of my Bandmaster) to minimize the hum, which worked well while messing with it.

ANYWAY, after I fixed the popping/dropout cold solder-joint problems, and fixed the broken wires I caused, and it sounded OK...I reassembled everything, and put his tubes back in, figuring it wasn't ideal to return it that way, and tell him to immediately get some new tubes and then deal with that. That's when I decided to check all the voltages on the diagram to see if they were close. That's when I noticed that -103V at that point, saw a resistor that is different from the schematics, and asked here. (Still don't know about that resistor, but apparently it's fine. Couldn't find a later schematic).

I was going to wait for some more info (thanks for the replies) before doing much of anything else, but decided this morning to dig out my little Mercury 1100 tube tester and do a simple check of his tubes. OOPS! One of his 6L6 tubes steadily lit up the "Grid Leakage Short" light! The other tube was kind of weak, but good.

Why didn't I check them BEFORE doing anything else? Good question. I'll take this as another "bonehead" lesson. I'll say the reason is that the amp was working, though kind of noisy, and the problem I was chasing was the cold-solder joints. The tubes both seemd to glow about the same. It just didn't occur to me that one would be that bad. Still, no excuse.

So, I put my tubes back in, set the Bias Test Point voltage to ~68mV, and it sounds fine, and that voltage in question is now -54V, about what it should be.

At this point, I'll give it back to him and tell him to buy some new tubes, and have those set up properly. I managed to repair his main complaint, and just stumbled onto some other problems. I know what some of you are thinking: "The dude has just enough knowledge to be dangerous!" Well, perhaps. But, if I was doing this every day, also, those "bonehead moments" wouldn't happen...so please go easy on me.

Thanks,

Brad1

PS...WHY do I log in to post, write the post, and when I try to send it, it makes me log in again...and I lose what I just wrote, unless I copy it before posting?

[Chuck H]

You must check the "remember me" box when logging in to stay logged in when writing long posts. Glad it worked out. Happy new year.

[Albert Kreuzer]

But, if I was doing this every day, also, those "bonehead moments" wouldn't happen...

Oh, yes, they would happen, believe me.
(Don't ask how I know)

[Brad1]

Advice for Tubes for the H.R. Deluxe...

OK, so he'll want to know what tubes to buy for this. He has said he wants fairly clean tone with some overhead, he uses only the clean channel, and he uses a Fulltone Full-Drive for some drive.

He's heavily influenced by SRV, and plays pretty much all blues.

Any good recommendations for reasonably-priced robust preamp and output tubes to get a clean signal with a bit of hair around it, that may respond well with that pedal (among a couple of other wah/delay/etc)?

Thanks,

Brad