Guild99J-$50find-PICS-SpkrDead,AmpScreams-PICS

[lostpick]

Tdpriers and beloved J. Crash,

Your assessment please...bought it last night..
contact cleaner works wonders...it loved my tube screamer and Yamaha Magic Stomp...
How do I get the full 40-50 watts out of this
circuit? It sounds a 15 watter that stays clean until I push the front end hard with a solid state pre-amp then it gets real loud, smooth and creamy but not too much break up..
Played thru 2x10 100 watt cab last night, at times dimed, not a stutter...

Check out the schematic pictures...I am thinking about a 15" spkr....I know that gives more low end,but volume also? LOUD Vistalite drummer compatibility needed....Can I get this to sound like the 59 Bassman ReIssue
I dream about? Ultimately will it be the tranny
capacities that bottle neck the output wattage?
Is a Celestion Vintage 30 too much spkr and
will slowly amp components?
Should I use a lower wattage Jensen or JBL??
I want to tweed the cab with a funky but chic
fabric with a 50s or Art Deco or Art Nouveau
vibe...Can the trem circuit be morphed into a reverb loop driver? Can it be used as an extra
gain stage? I could even live with no circuit changes as long as I know that driving two
50 watt speakers by pushing the front end hard is not slow killing this amp...





















Hey Guys... help me get my head on strait with with a good restoration plan...my vintage
AC30 is going bye bye, and this has to keep
me happy

[johnnykf]

So that's where Steve Carr got that cool looking cabinet idea from!

[JohnnyCrash]

NIIIIIIIICCCCCCCEEEEE!!! What a steal!

It looks like she's Cathode biased... you could squeeze 40+ watts out of her with a fixed bias and a new output transformer.

If you're not going for "resale value", I'd build a new cab for it, if I were you. Man, what a cool little amp!

Otherwise, I'd try to keep it original.

Personally, I'd drop her into a new cab though... how's the stock speaker sound? Tweed is too passe for that amp! I'd do something unusual, but still very '50s...

--

You know what - I take it back, here's what you should do:

Keep that amp all original.

Then, build an exact copy, except fixed biased for a 50watt version.

That looks a little similar to the 5D8 Twin circuit I'm building - 4 inputs, cathode biased pair of 6L6's, basic 12AX7 phase inverter... except of course the Tremolo, single 12AX7 preamp, 12AX7 trem driver.

MAN, that preamp section is so much more basic than the 5D8, that makes it really cool in my book!

I just drooled all over my shirt... damnit... HAHA!

[lostpick]

Think the coil fried - smoke or dust, couldn't tell - this is a Oxford alnico 12L5N-2 - power
rating anybody?? I need a workhorse spkr in this?? May be someone wants to trade me something for the Oxford that needs a rebuild? Would a muffin fan pointed
at the output tubes and speaker tranny buy me some headroom before I get my plan together?
Is constant heat the issue with overloading spkr trannys or do the windings just spontaneously evaporate like a fuse or do they short out fron die-electric breakdown...
What do ya think bout a 15", cant fit 2-10s..
I was getting at least 30 watt performance
with a 2-10 cab I hooked up...and stuffing the front end with pedal and it stayed tube pre amp clean but heard nice power saturation that complimented the pedal ...I am hearing that the trem on these amp are precious, and I have one song I wrote that uses a Smith's -How Soon is Now- trem vibe - so Im gonna keep stuffing the front end...very excited...
haven't smiled this much in years

[Sidney Vicious]

Super cool cheap score!!!

[Bill Ashton]

You have to remember, these amps were being built for jazzers, so it will probably be mostly clean unless moded.

There is some (unfounded?) info floating around that these were either copies or built by Ampeg during that era.

I have a 66-J, with a slightly different cat, but the control panel is almost identical. Mine came (when I got it in 1968, used) with a blue Jensen P12R, which I promptly changed out to a (Radio Schack) Jensen RSC12N and she was (is) wonderful. I would have said the Oxford wasn't original, but clearly the Guild sticker is on it.

I'd love to get a copy of that schematic, simply for comparison to my 66-J diagram. I can email you a catalog cut of a slightly later 99-J in exchange? The cat. says it is 30 watts...

[Bill Ashton]

...while all your photos were loading, so I didn't see the bit about the speaker dying. Too bad. Anyway, I have images of 99-J's before and after your style...a half tweed version has a blue Jensen with bell cover, the later cabinet style like mine, has a blue jensen with a small ceramic magnet...the resolution is not good enough for me to read which model.

I had some trouble with mine after a cap job and addition of three wire cord, as it kept tripping the GFI in my basement. The members here sorted me out, and a removal of the "death cap" resolved the issue...I see yours has one, I believe its the red cap on the little terminal strip where the ac comes in.

Save that frosted green pilot lite cover, you'll never find another!

The tremolo on mine was great, but died over the years, even a cap job didn't get it back, now its very subtle.

I was able to look at your schematic, and while the rectifier are different from my 5Y3 and 6V6's, the topology is the same...one half of one 12AX7 for each channel, one whole 12AX7 for tremolo and one 12AX7 for phase inverter. I am only guessing here, but presume that the single gain stage is what makes for such a clean sounding amp.

Only other difference in your and mine is that I have a "bright" input on one channel and no "mike" input.

Have fun with her...be careful, looks like all original caps...

[Bill Ashton]

which one is the current or last one...???

[Uriah T.]

I echo Johnny Crash in that that amp will not get 40 watts easily... the OT is too small and it's cathode biased. But those are the things giving it that great crunch when pushed hard.

You aren't hurting anything by pushing the front end, as long as the speaker can handle it. For originality, you could put an old Jensen P12R or the like in there, but you'd surely blow it the way you're playing it. A Celestion Vintage 30 wouldn't fry the amp, and it would hold up. But try a Weber 12 or Reverend Alltone in there for a more vintage American sound, with better volume.

Unfortunately, it won't ever sound much like a tweed Bassman (transformers, circuit, cathode bias)- also try new JJ preamp tubes, they are a little higher gain than what's probably in there now. There is probably an unused gain stage in there (half a 12AX7), and a lot of folks have modded their old Supros and the like to use it. Personally I like the sound of pushing a simple gain structure.

Good luck, and good score; I always dream of finding something like that at yard sales...

[Bill Ashton]

http://www.weberspeakers.com/weber/csig12.htm

As close as you are likely to get...economically...to the Jensen C12N that you will need.

There are no used half 12AX7 sections in this, its real simple, sort of like a wide panel Fender, but [/i]way cleaner in output. I can't comment on how the output tubes are biased, don't have that level of knowledge.

I think you are probably doing the right thing, using a pedal in front of it.

My opinions come from its little brother (sister) mind you, but the only time I could get the slightest bit of "hair" on mine was using some 50's Delco unmatchted 6V6's...

[Bill Ashton]

I meant "there are no unused half 12AX7 sections."

Don't know what happened with the italics thing...

[lostpick]

and send it to ya Bill.....appreciate your detailed feedback. The Weber looks like what I am after.
Looks better than the Celestion Rocket 50 that
the GC salesman keeps pestering me with....
There is also a Celestion Heritage, 30 watter on Ebay
but I think I need a 50 watter....

[Scott S]

I'm digging the Baxandall tone controls -- those will knock down a bunch of gain, but they're so much more useful than the Fender stack.

Record some stuff when the amp is working again!! :D