HELP needed - installing an output transformer

[bad daddy deville]

Success!

I powered up the Galaxie 10 today with its brand new Output Transformer and... it sounds terrific! When I first got this amp (a friend snagged it from a yard sale for $25) it sounded horrible. I replaced the power tube with a JJ6V6S, which got rid of the squeal, but that only revealed other problems. I put in a Tungsol 12AX7 preamp tube, and replaced the stock Celestion Tube 10 speaker with a Weber Signature Series Ceramic 10.

The results were still unacceptable--- nasty, harsh highs and a "flubbiness" to the bottom end. Overdrive came out as just "fizz". It sounded so horrible I decided to sell the amp locally, but thinking about it, I knew I'd only get a hundred bucks or so. Then I remembered a discussion here at amp garage.com about how the output transformer was a piece of crap and should be replaced. I figured I'd already sunk time and money into the amp, so I should give that a try, and man, am I glad I did.

Hot mids, tight bottom end. A little treble-y, but nothing that rolling off the Treble knob doesn't fix. Crunch that sounds crunchy, not fizzy. I believe the amp's sort of a Fender type design, but now it sounds halfway between a Fender and a Marshall, if that makes any sense.

Martin, you mentioned that if I used the 7KΩ tap I could use a 6V6. I'm already doing that with the 5KΩ tap. Should I switch to the 7KΩ one? It'd be easy enough to undo the splice I did and splice in the other one.

Once again, everybody, thank you all so much for all your help. And as a way of expressing my gratitude, here is some Transformer Porn:

[img1051]http://www.hallamgallery.com/silvertone/collider.jpg[/img]

[img:877:629]http://www.hallamgallery.com/silvertone/EXEF1.jpg[/img]

Look at that thing! That's in a three-channel guitar preamp built in 1990 in Germany, called the Triton. It's a wonderful sounding piece of gear which I use as an amp, going right to a speaker cabinet rather than to an external power amp. It's old and has some hum to it, so now that I know how to safely discharge the voltage, I've decided it's time to replace the caps. When I took off the cover and saw that transformer, I thought at first it was the Large Hadron Collider.

[img494]http://www.hallamgallery.com/silvertone/EXEF2.jpg[/img]

[martin manning]

Success!

Great!

I believe the amp's sort of a Fender type design, but now it sounds halfway between a Fender and a Marshall, if that makes any sense.

The circuit is kind of like a Champ on steroids, with extra controls. It runs higher voltage, a solid-state rectifier, has a TMB EQ, and it was designed with a 6L6 (instead of a 6V6), and a 10" speaker. It also has a master volume so you can turn up the preamp distortion while keeping the overall volume down.

Martin, you mentioned that if I used the 7KΩ tap I could use a 6V6. I'm already doing that with the 5KΩ tap. Should I switch to the 7KΩ one? It'd be easy enough to undo the splice I did and splice in the other one.

On paper 7K is a better match for a 6V6 at the voltages listed on the schematic. As long as you don't see the tube's plate (the box-like structure) glowing red while playing it should be ok at 5k. I would try it at 7K, expecting to get a bit less distortion, maybe tending back towards the Fender sound. You could also try a 6L6GC at 5k and see if you like it. I'd expect to get a nice clean tone and more headroom with that arrangement.

That preamp is a nice piece of gear. I'd say at ~33 years old it is due for new power supply caps. Be very careful desoldering the old ones from the pcb so you don't damage it. Did you get some desoldering braid yet?

[Leo_Gnardo]

Good going bad daddy!

On your German Triton - that rack of 4 transistors across the back with substantial heatsink looks a lot like a power amp to me. Especially since it drives a speaker cab directly. Toroidal PT gives it that futuristic look. (It's just a mini hadron collider. Everybody should have one.) Some other manufacturers have gone to toroids - Egnater, Laney for instance.

[bad daddy deville]

I think I'm going to keep the 6V6S at 5K, since I prefer the crunchy British vibe it's got to the more Fendery sound. Supposedly, the 6V6S can "handle handle higher plate voltages"---at least, that's what they said at thetubestore.com where I bought the thing. Of course, if it starts glowing red I'll switch to the 7K.

About the Triton--- I don't have a schematic of it and the company is long out of business. There's practically no mention of it on-line. I don't even know what wattage it's rated at, though plugged into a 12" speaker cab, it's quite loud. I guess if you're in an arena rock band you send the signal to a monstrous power amp. But as Leo points out, with an 8Ω speaker out, is that the kind of signal you'd put into another amp input??

I have my desoldering braid. Now I'm trying to find replacement filter caps. The ones on the circuit board are ADE brand (W. Germany) (that's how old they are!) 2200 µF 63V- 40°--105°C.

I bought a VOX speaker cabinet on sale. It's got one 12" speaker. The Triton is a rack-mount component, and I have a 2U rack it can go in, but I'm thinking about cutting a long rectangular hole in the top of that cabinet and lowering the Triton down into it---thus creating a combo amp. I have a 12" speaker I can use that'll take the power from the Triton amp. The VOX cab was meant to go with the VOX TV4AC amp head, which is rated at 4W, so its speaker probably wouldn't survive the output of the Triton.

[Leo_Gnardo]

About the Triton--- with an 8Ω speaker out, is that the kind of signal you'd put into another amp input??

I expect your Triton has a line out - that's where you'd run a power amp from. Big stages - for electric guitar usually there's a mic on the guitar speaker rather than taking a signal direct from the amp. Acoustic guitar - DI and/or mic on guitar. Bass, DI sometimes supplemented with a mic on the speaker.

Like your idea of making a combo or you could just rack up the Triton & save the carpentry. Also any cab rattles that may result from slinging an amp into it. Think about it before you break out the saw. Yes a heavier duty speaker is called for, now what to get? So many choices. Listen to whatever you can, & if something appeals to your ears, get that.

[bad daddy deville]

That's the thing, Leo_Gnardo, there is no line out. There's a jack labeled "Speaker 8 Ohm" with a lightning bolt next to it. There are and EFFECTS SEND and EFFECTS RETURN. And jack for a channel switching foot switch. There are holes, filled with plastic plugs, for MIDI IN and THRU connectors that must've been an option, and a plastic plug filled hole for an uninstalled WAH connection ---whatever that would have been? So, how this was to have been a preamp is a mystery.

And as a single space rack item (which was probably why they put a low-profile toroidal transformer in it) it makes an ungainly size for an amp head.

Before I dig into that VOX cab, I can just connect the Triton to it as an external speaker and play through it REAL LOUD to see if there are any rattles lurking inside.

[Leo_Gnardo]

That's the thing, Leo_Gnardo, there is no line out. There's a jack labeled "Speaker 8 Ohm" with a lightning bolt next to it. There are and EFFECTS SEND and EFFECTS RETURN. .

Effects send may amount to the same thing as a line out. Only 1 way to find out whether your EQ and master volume show up before or after the FX send, gotta try it.

With no info from the company, we don't know whether the power amp is a "floating power" type, popular in the time frame the amp was made. If it is, sure fire damage if you attach the speaker output to anything grounded. One fast way to tell, with amp off, put one ohm meter lead on the speaker "-" or "common" connection and the other on a known ground point - chassis or AC power ground. Zero ohms? Then your amp isn't a floater. No connexion, or high ohms, assume it is a floater and don't connect speaker outputs to anything grounded or else kaboomski.

[bad daddy deville]

Okay, Leo_G, I plugged the amp in (power off) and connected a speaker cable to the speaker output. I set the ohmmeter on ohms, and touched one probe to the ground part of the speaker cable plug, then touched the other probe to various parts inside the amp that were touching the frame, like the backs of some of the potentiometers, etc. The ohmmeter's reading of 0.0F never changed.

Then I unplugged the power cord, and touched the other probe to the ground lug (I guess you'd call it) of the socket that the power cord plugs into in the amp. The ohmmeter responded and gave a reading of 11.2 (fluctuating around that number.)

Uh... now I'm confused. What do you think? Floater or not a floater?

I have to apologize for my ignorance about electronics. I've tried for years to understand the underlying principles, and can ~almost~ get it... but then something happens and it all slips from my grasp. My son's an aerospace engineer and doesn't get it that I have a sort of learning disability about this stuff! Anyway, at 64 years of age, I've figured out how to work on things without totally understanding what's going on, and a large part of that strategy means relying upon help from others.

[Leo_Gnardo]

Okay, Leo_G, I plugged the amp in (power off) and connected a speaker cable to the speaker output. I set the ohmmeter on ohms, and touched one probe to the ground part of the speaker cable plug, then touched the other probe to various parts inside the amp that were touching the frame, like the backs of some of the potentiometers, etc. The ohmmeter's reading of 0.0F never changed.

Then I unplugged the power cord, and touched the other probe to the ground lug (I guess you'd call it) of the socket that the power cord plugs into in the amp. The ohmmeter responded and gave a reading of 11.2 (fluctuating around that number.)

Uh... now I'm confused. What do you think? Floater or not a floater?

First set of measurements tells us it's not a floater. Can't imagine why it would be different with the power cable unplugged. However you did measure ohms between the speaker "-" and the AC ground, not other presumably grounded parts of the amp. Possibly there's a resistor separating the signal/chassis ground from AC ground. I've seen that sort of thing rarely in hi fi gear, Dynaco preamps come to mind - they had a 10 ohm resistor between circuit ground and chassis.

[bad daddy deville]

Whew! It's reassuring to know my amp isn't going to go kablooey! Thanks, Leo_Gnardo!