NAD! Guild 99-J

Bill Ashton

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Yesterday while passing through Worcester, I stopped at our favorite guitar store in the heart of New England to pick up some LaBella strings...looking to the back of the store from the counter I nearly soiled myself :shock: ...either they had taken in a Carr Rambler or...or...could it be? YES! A Guild 99-J :eek: :eek: :eek:

Well, after a longing discussion with SWMBO over the cell, I called them back and asked them to hold the piece for me. After a long drawn out morning, I was able to get back...Rivera 55-Twelve in hand to put on consignment...for a close examination in daylight.

She was not nearly as pristine as I thought her to be...although can't say you could find one much better...silver grille cloth is squeaky clean and tight as a drum. Handle pretty good, tolex or whatever outstanding, though around the bottom getting worn...due to 3 bad feet :( Cranked her up with a lovely G & L ASAT CLassic (in antique white with dead-turtle PG) and WHOA! Guess there ARE 6L6's in this puppy, nearly took my face off...loud, proud and clean. Alas, bit of a hum, though more like one was playing under flourescent lights...uh, I was...tremolo doesn't work :cry: :cry: But overall very very nice. No cover, no footswitch. Brought into the store by a son-in-law, the owner having passed...was he a "jazzer" I asked...the Polytone sitting next to her answered that question.

Well, what to do. Price negotiable? Yes, they will call the owner. Should I or should I just take it...I had already planned on a cap job, so had that figured into the selling price, but because the tremolo didn't work I offered $50 less...a few minutes later, it was mine.

Got her home and find a GZ34 rectifier (made in Holland, no other markings), pair of JAN/Sylvania 6L6WGB's, an RCA 7025, JAN Sylvania 12AX7WA and a Magnavox (!!) 12AX7/7025. Store repairman butchered some caps into her, cannot tell whether this is for the power supply filter or not, and do see one electrolytic getting ready to sh%t its load (see the fiber board, far right hand side. Based on the last, I don't know if I dare play it much more tonight.

I believe the speaker to be an Oxford (12L5N-2), and she sounds very good, tight bass at least with the tele. Will need a 3 wire cord and plug, and it is overfused with a 4 amp slo-blo.

So, just have to decide whether I should order up the caps from Mouser and get to it or bring it to my local tech...don't know if I will sleep well tonight :lol:

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dapmdave

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Beautiful, Bill! Great score and another Guild rescue.

Dave :D
 

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Yeaaahhhhhh, Bill. Looks like he used the old cap cap as ties points for whatever caps he buggered in there. I would chage that bad wax cap on the board for a new Mallory of whatever value is in there, replace those minimites with 25mf/25 volt electrolytics and just get a new cancap from tubesandmore.com

Looks like a fairly easy amp to service, gratz on the score!

Looks out of stock at AES, fliptops has a 20x20x20x20 cancap.
Tie two of the lugs together to make a 40x20x20 and you should be golden.


http://www.fliptops.net/catalog/product ... cts_id=208
 

capnjuan

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Hi Bill and congratulations on the amp! Too bad about the feet ... :( :wink: It's about as clean as I've ever seen.

As for all the business at the rectifier end ... I'd rather not see the old can cap used for tie points ... the old caps in the can are still hot and in parallel with the new caps; if the old sections go/leak, then this will have to be re-done. Also, I can't tell what the old brown cylinder electrolytics underneath are doing still there; one ought to be the 6L6 cathode resistor bypass cap (100uf/25V on the schematic) but it should have been changed out ... vintage is nice but arguably trumped by better functionality and reliability.

As Steve said, the two MiniMites at either end of the circuit board have to go; they are cathode resistor bypass caps and it's the fate of old electrolytics to leak or blow sooner or later. Also, SweatyBoy at the far right; that's the filter cap for the preamp power ... 10uf/450V ... value is fine ... bigger only gets you a risk of the boomy thing. Seven times out of ten, no trem is a function of worn out trem caps shown in the blue boxes below. Like reverb, trem is always tremming away whether it's turned on or not; over time, the pulsing DC wears the caps out. I wouldn't mess with the disc-shaped silver mica cap ... they last forever.

Guild99Jcb03.jpg



If you're thinking about DIY, if you have an inspection or dental mirror, you should look to see if you have a bunch of jumper wires on the bottom of the board. If you're doing the work from the top and heat up the solder joints, the wires underneath can fall out and you won't know anything's wrong until you power up. Even then, you'll look at your new work and not see anything wrong. The workaround is to drop out any jacks or controls that are wired directly to the board ... you can then tip the board up on its side and see both sides ... much better for avoiding screwups.

Like I said, I don't see that the 6L6 cathode resistor bypass cap has been updated; if you're going to straighten out the preamp caps, now's the time to see what's what at the other end.

Just a great-looking amp; should we be looking around for some other GM metalwork for decorations? Like those faux fender-mounted exhaust ports on '50s Buick Roadmasters? Congratulations; it's a beauty! 8) 8)
 

Bill Ashton

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Thanks, Cap' ! I was hoping you would chime in! I think I have a bunch more questions for you, just have to organize them...

Here are a couple of images to show the relative sizes of the 99-J v. 66-J...yes that is a Weber speaker in the 66-J, its blue Jensen P12 is boxed safely away...

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P2110005.jpg
 

capnjuan

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Weber speakers remind me of certain brand of guitar ... great cost to value relationship. Assuming we can find another Oldsmobile hood ornament to straighten out the 66J, this is what I'm proposing for the 99J ... each would go in a corner of the grill ... Okay ... I don't know what you'd do with the rest of the car ... put it on eBay?

Will do a closer look at the rectifier / old can cap end ... I don't understand what the extra old brown cap is doing there and, if you get a chance, can you twist those two paralleled resistors around a little and tell me what the resistance values are?

Guild99J55buickexhaust.jpg
 

capnjuan

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It is a great-looking amp ... but with some funny business going on downstream of the rectifier. Counting capacitors on the schematic; (1) is the primary/first 40uf/450V filter cap seen by the rectified DC normally connected to the center tap of the output transformer and a dropping resistor ahead of the screen supply (2) screen supply 30uf/450V (could be 20 ... schematic a little murky) filter cap providing filtering for the 6L6 screens. Tapped from that cap (3) the 10uf/450V preamp and tremolo supply filter cap. (4) is the 6L6 electrolytic cathode resistor bypass cap ... that's 3 / 450V electrolytic filter capacitors ... either individual ganged in a can and 1 20uf/25V bypass cap or 4 capacitors at, near, or part of the power supply.

powersupply02.jpg



However down at the business end of the chassis, there are at least 7 or maybe 8 capacitors ... either can cap sections or individual caps:

powersupply01.jpg


Sometimes the can caps have an extra dead post; the larger the capacitance of the sections, the larger the space inside the can consumed by the cap section. If this was a 40uf/30uf/10uf can cap, it's possible that one of the posts is just a tie point; if not, it's hot and there are 8 caps (and one on the far right of the circuit board) for as many as 9 caps when 4 are called for on the schematic.

Before I forget, the two new caps that are wadded together have their grounds tied up somewhere at the extreme right of the chassis. Best practices is to ground them all at the same point ... save possibly the preamp filter cap ... to mitigate hummbuzzeroo caused by a ground loop.

Can think of two reasons for the overpopulation; somebody wanted a 'quick and dirty' cap job so the new sections were put in without disconnecting the existing - or - somebody thought they'd 'beef up' the power supply with added capacitance so they intentionally left the existing stuff in place.

However, all rectifier tubes have design capacitance limits at the input of the filter; for the 5AR4 that limit is 60uf/475V. If that 47uf cap is in parallel, for example, with a 40uf/475V hot section of the can cap, then the filter input capacitance seen by the 5AR4 is 87uf ... not 60uf. :shock: If any of the older stuff; the can sections or the two loose brown cylinders are connected and start to fail, than all that has to come out of there. :(
 

Bill Ashton

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Hello all, had a chance to look over the 99-J for a few minutes today...

The big wax cap behind the conglomeration of capacitance and silicon gunk is
apparently the death-cap on the AC line in...it goes from the ground tab on the
big cap cap to the fuse holder.

What was not seen until I gingerly moved the mess with a chopstick is:

P2150003.jpg


Yeah I guess this is overfiltered :shock:

Also it looks to me as though one of the resistors crossing a cardboard electrolytic is cooked or very nearly so...see the image above of the tag-board, the brown Mini-Mite that Cap'n has labeled as a 12AX7 bypass cap...

The little cardboard Mini-Mite that is just peeking out from behind the sand-filled resistors is a 25 Mf, and goes from Pin 8 on the first 6L6 to a terminal strip connection which I think is ground...can't tell, too much stuff in the way. Not much luck finding it on the schematic :(

Those paralleled sand-filled resistors are 10K, 5%'ers.

With the family emergency situation I have going on right now, as much as I want to do some of the work myself, I think she will just go to my tech...because I do want to be able to play her as much as I want to fix her!

I found a page excerpt from a Guild 1962 catalog that shows this amp (dated March '62), so that feels about right, as I presumed my 66-J couldn't be older than '63 sometime due to the date codes on the pots. In this thing the EIA codes seem to be all over the place.

Anyway, thanks much for all your observations and good will!
 

Walter Broes

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That looks great, congratulations!

I'm seriously wondering how much power these put out, not that I'm in the market for one *right now*, but if it has a little more headroom than a typical tweed Fender Deluxe, I'd be very interested in looking for one of these some time soon.
 

Bill Ashton

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Walter...headroom is what these amps have...if you are looking for Fender Tweed Deluxe distortion, look elswhere! My 66-J, from day one in March of 1968, was clean right up to max...never used it above about "5" really...even with a new RSC12N, clean clean clean, sorta more like a Fender BF/SF Princeton. I wondered what the 99-J would be like and its the same pretty much, but done with 6L6's...nearly took my face off in the shop. Once she is all set, I cannot wait to try my new OCD pedal on 'er...with a new speaker of course!
 

Bill Ashton

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...oh and by the way Cap'n, I do have the remaining star for the 66-J...fell off at one point but I saved it...just don't know what kind of glue to use to get it back on!

My first though was Oldmobile (the stars), but now I am thinking '59-'61 Pontiac Bonneville...or maybe Star Chief?
 

capnjuan

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Hi Bill; first things first ... the amp can wait ... or just get somebody to look after it. So ... the final count on cap sections is around 37 or 38? :wink:

The best solution would be a replacement can cap ... 40uf / 20uf - or - 30uf/ 10uf @450V. Next best would be a two-section can ... lots of those around ... with the preamp filter cap mounted on the circuit board like it is now. Next next best would be cobbling together something like this:

ps07.jpg


... using wiring strips which provides mechanical support and the ability to combine grounds and take them to one point ... wherever the center tap of the PT secondary is grounded. Individual sections always present orientation problems ... how to get them mounted where they need to be, physical support (see use of goo in the pics), and getting them grounded. In any event, I'm sure your tech will have a good solution ... which probably won't involve adding fender skirts or foam dice hanging from the rear-view mirror :wink:

Walter: I listened to Bluesy's 66J once ... didn't get it past 5 or 6 but it was pure Ampeg ... not the slightest hint of breakup .. it was also cathode-biased like the 99J. Everitt Hull, founder of Ampeg and whose background was as a bass player, was as committed to the clean thing as Ted McCarty and Seth Lover were at Gibson. They didn't care if Gibson's student amps broke up early but, like Ampeg/Hull and unlike Fender, their higher-end designs were intended to minimize 'wolf tones'. Not sure how much of a leading edge these amps have.
 

Bill Ashton

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John, I was going to ask this on a different thread, but just as well to do it here.

What should I use for a new line cord. While I am sure #18 conductors are fine, there are so many ratings! When I did my 66-J I used SJO with a hospital connector on the end, in retrospect way overkill. What would you suggest, and what does SJO, SJOW and the different temps in C mean? Is 105 deg C "better" in this use than 95 deg C?

Thanks!
 

capnjuan

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Bill Ashton said:
... What should I use for a new line cord. While I am sure #18 conductors are fine, there are so many ratings! When I did my 66-J I used SJO with a hospital connector on the end, in retrospect way overkill. What would you suggest, and what does SJO, SJOW and the different temps in C mean? Is 105 deg C "better" in this use than 95 deg C?
Thanks!
Hi Bill; 3 conductor #18 is fine and any of the cords regardless of the specific type; SO, SVT, SJO, SJOW ... will be okay. Type refers to the type of insulation and heat resistance. I think the least rated is Type SO and it's 95 degs C ... hot enough to boil water ... yes, hospital grade plugs are overkill.
 

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capnjuan said:
Walter: I listened to Bluesy's 66J once ... didn't get it past 5 or 6 but it was pure Ampeg ... not the slightest hint of breakup .. it was also cathode-biased like the 99J. Everitt Hull, founder of Ampeg and whose background was as a bass player, was as committed to the clean thing as Ted McCarty and Seth Lover were at Gibson. They didn't care if Gibson's student amps broke up early but, like Ampeg/Hull and unlike Fender, their higher-end designs were intended to minimize 'wolf tones'. Not sure how much of a leading edge these amps have.
I've been reading up on these, googling some, and apparently they have a Baxendall tone stack, like the "King of Clean", the Standel tube amps from the 50's - and apparently, according to something I read - that robs the amp of the preamp gain a typical narrow panel tweed Fender would have.

If those Guilds are so clean, sounds like a JBL speaker might turn them into a somewhat of a mini-Standel amp, maybe. :idea:
 

capnjuan

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Walter Broes said:
capnjuan said:
Walter: I listened to Bluesy's 66J once ... didn't get it past 5 or 6 but it was pure Ampeg ... not the slightest hint of breakup .. it was also cathode-biased like the 99J. Everitt Hull, founder of Ampeg and whose background was as a bass player, was as committed to the clean thing as Ted McCarty and Seth Lover were at Gibson. They didn't care if Gibson's student amps broke up early but, like Ampeg/Hull and unlike Fender, their higher-end designs were intended to minimize 'wolf tones'. Not sure how much of a leading edge these amps have.
I've been reading up on these, googling some, and apparently they have a Baxendall tone stack, like the "King of Clean", the Standel tube amps from the 50's - and apparently, according to something I read - that robs the amp of the preamp gain a typical narrow panel tweed Fender would have. If those Guilds are so clean, sounds like a JBL speaker might turn them into a somewhat of a mini-Standel amp, maybe. :idea:
My understanding is that Baxendall tone controls preserve more preamp tone that do conventional bass and treble controls (I guess that means Fender) that dump signal to ground ... "tone-suck" in the vernacular. Since nothing is free maybe less gain is the trade-off for the more sophisticated controls.

The schematic doesn't ID any voltages but the cathode-bias, depending on this and that, will limit the output to 25-30 watts. A JBL would go a long way in this amp but then JBLs tend to flatter anything they're in!
 
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