2nd Hand Homemade Amp

[HommeMarrBuckley]

Hello all,

I probably have the answer to this already as a big stay away but wasnt sure and thought to hear some opinions from experienced builders.
There's a guy with an old PA school amp that was converted to a 60s vox guitar amp (but not a specific model).  It's not working due to the blown original pt.  He had someone build it and doesn't have a schematic or layout.  I thought maybe it's something along ac4. It has a 12ax7, el84 and ez81 rect with pentode and triode switch that goes 7-14 watts--this possible?  It has multiple taps . The board looks ok with newish components (although I don't know if they were damaged with the blown pt)  This guy doesn't seem to have the time or patience to deal with this and I think it could be a decent project for a noob like me (to annoy forum members on this board for finding solutions--hah)

I know it doesn't sound good for someone with limited experience without having any kind of schem or layout to go on.  I am not sure how to determine a proper replacement pt and even so it could still sound awful if the design is off.  Hes asking 150 but I don't think I will pay that with so much unknown.
 
Just wanted to hear some thoughts and opinions from members here if it's worth the effort.
Thanks

[tubeswell]

Its not worth that much if its not working IMO

[TIMBO]

Hey tubes, "tell'm hees dream'n". 

[John]

My 2 cents: I wouldn't pay more than $50 tops. PT is the single most expensive part in an amp. And there's always the question of why the PT blew to start with. You can buy carcasses on eBay for way less and usually the trannies are good.

Be aware though, once you dig your mitts into an old tube amp, you're hooked for life.  The smell of old wire and 50/50 solder messes with your brain.

[eleventeen]

$150 is silly ridiculous. I am assuming that for that money, you get a non-working thingy in a metal-cabinet that is not friendly to being dragged around--in other words, is fragile.

I again bring up that one can buy a used Peavey ValveKing 112, a 50-watt amp that I am having a good time with (having replaced the OEM speaker which is admittedly a piece of junk---but not completely unusable and which would make a perfectly acceptable test-bench speaker) for $200-$250. For that money, you get a rugged and travel-worthy amp (and believe me, the thing is very well built, and I have as much or more hesitation against the Peavey badge as anyone here) with a handle and metal corners and with reverb and channel switching...

I am perfectly fine rebuilding PA amps etc; for geetar use, but even if your labor is free (in exchange for the learning experience) the economic calculus ought to be performed that while fun is fun and learning is learning, you are going to have to spend $100 for:

One or the other transformer
Pots
New tubes
Pile 'o parts

and if you have lots of those type parts lying around, good for you, but you still end up with a kludge.

IMHO, you are far better off finding a dead solid state amp like on this thread, http://www.el34world.com/Forum/index.php?topic=15734.0 and making something rugged and transportable. For just a little more money, maybe....and I would bet that virtually any music store has a dead SS amp sitting in the back they would sell for $25...or you could advertise locally WTB dead SS amp.....and get a cab, chassis, and maybe a speaker....for under $50. Maybe free (like I have done 2x in the past month) And then you can rip the guts out and start fresh with a KNOWN parts cost to get THE WHOLE THING.

My .02

My only point is, I myself do not care how much money you or anyone else spends on whatever project you wish to build, but if you are telling me that you are saving money by paying $150 for your carcass and then tweaking it out for another $150 and then you have a 1967 Bassman head, color me skeptical.

[Slimtim]

Yeah that seems a high price to pay for a broken homebuilt.

[PRR]

> Hes asking 150

Wish him luck. WELL promoted on eBay, on the right week, I've seen such things bring near that much; but rarely.

If the price slips to $50, it *may* be a fun project. Being two (?) EL84, the PT is easy, any "18W PT" will do. Being PA, the OT may or may not be terrific for guitar amp; it may be too big and "too clean", OTOH there were some junk PA OTs.

All small audio amps are 98% the same. You got your OT to your power tubes, power tube grids are driven by a driver, usually a preamp before that, and power sources to the various stages. The tone-controls are mostly where guitar amps diverge from PA custom; you can bypass that to get it working and then play around with various ideas.

[HommeMarrBuckley]

Thanks to all that posted.  I think $75 is reasonable.  I dig put things in a negative light but in terms of a gutshot, things looked pretty good and if you were to do a price point it would be pretty close.  The chassis and frame was a large piece of squarish steel with handles and it had a locking, old school carrying case.  Regardless, I will see what the guy says.  Something tells me anything less is a loss for him but I think it's inevitable.