Jersey Girl

[littlesongs]

Wow cap'n, my posts feel so inadequate after reading yours!

+100

I really appreciate the patience and guidance John. It makes a whole lot more sense now.

Hi Dave; first things first ... have to salute Guild. It made the RC20 Remote reverb/tremolo unit sometime in the early 60s (Hans or Kurt for dates). As Jeff pointed out about the EJ, it too relies on a dry signal from another amp tapping its signal at its speaker:

Cool history! It would be interesting to suss out when the Gibson & Guild designs hit the scene. The Ampeg Echo-Satellite debuted in '61.

The signal heads to pin 11 - the grid of stage 3 ... amplifying stage and phase inverter from where it goes to the 7591s each getting its half of the AC waveform. I'm not completely sure about J2, the auxiliary input ... possibly a mic for yodeling; and I don't understand the function of the shorting arm there but so far, I don't have too.

The power in the amp shown below; in the lower right-center, all the taps on the transformer; red for high voltage secondary AC, yellow for 5VAC heaters for the 5Y3 rectifier, and green for the 6.3VAC 7591 and 6D10 heaters. Shown far left the current filter caps and dropping resistors.

The primary DC (red) goes to the center tap of the output transformer and winds up on the plates / anodes of the 7591s. The magenta is power for the twin screens (pins 4 and 8 ) which are jumpered together. The blue is the power to three sections of the 6D10.

Thanks for showing me the ins and outs of the "plumbing" in there. I will definitely try yodeling when we get it put together. :lol:

The power supply with all the transformer taps ID'd and the three filter caps on the left (more on filter caps below). Note the 'yellow' cap that doesn't match the others and how its red lead touches the already-scorched power resistor:

Whoever put that yellow cap in didn't bother to straighten the mess out - see left below. On the right are listed all the pieces and parts that connect to pin 8 of the rectifier and on the left, how tidy and neat the work appears:

Edit: my screw-up. No high voltage AC on pin 8: should read:

The pin marked A is unused by the tube but Ampeg used it as a convenience tie point for one leg (white) of the incoming 110V service, a black wire leading down and away to the 'death cap' (the lead is sleeved), and the black wire (right center) marked '105' that feeds one side of the transformer. Whoever put the 'yellow' cap in by laying the new (red) capacitor wire on top of the high voltage DC (+/- 325 volts) coming out of the rectifier, left it within a gnat's a__ of the incoming 110VAC :shock: :twisted: :shock: Slosh some water/wine/beer/Stoly in there or get a whopper spike and an arc ... not good.

I might be tracing things out wrong, but if there is proper strain relief, I'd rather go straight from the new cord to the fuse rather than use an extra pin on the tube socket. Would that be wise? The little yellow 600V Cornell-Dublier is the "death cap" and it's gone for good with the new power cord, right?

I'm proposing something like this; a small rack made of two wiring strips; upper center is the ground side, upper right the hot side. The two dropping resistors; 1K/10W and 22K/1W can be mounted between the lugs on the hot side with leads already in place when the unit is dropped in .. one .. maybe two holes drilled in the chassis:

One way or the other, the condition at the rectifier socket has to get cleaned up.

I love that idea!*

It is the perfect blend of modular design and point to point construction. Drilling an extra mounting hole or two is no big deal. There will be plenty of room for it once things are cleaned out.

How does this parts list look?

Three 20uf 600V electrolytic capacitors
Two 5pt center ground terminal strips
One 1k 10w wire wound resistor
One 22k 1w carbon resistor
One heavy duty three prong power cord

(*It leaves me wondering why the heck they didn't do it this way in '65. If they weren't gonna go for a three stage can in the Jets, this would have been easier to assemble in quantity and mount in the chassis with a certain amount of haste. On the other hand, I've read the designs were altered to fit the current state of parts supply rather than the concrete plans of the engineers. It could explain the 40uf typo on the schematic too. That error corrected itself since tube rectification was out of the picture when the J-12-D and EJ-12-D came out a few months later. )

The tube I may need as a spare someday is a 6D10.

10-12 bucks at the tube retailers!

Add: I'm grabbing a copy of "The Guitar Amp Handbook" too.

 

[capnjuan]

... Cool history! It would be interesting to suss out when the Gibson & Guild designs came out. The Ampeg Echo-Satellite debuted in '61.

This is Gibson's GA1RT / remote reverb in its first iteration late '50s/early 60's; dry signal from another amp into a reverb can; 8" speaker, tremolo, 12AX7, 6BM8, and a 5Y3 rectifier. Guild's RC20 almost part-for-part the same except a 10" speaker and diode rectifier. Gibson later upgraded this amp (to the GA1RVT) by adding a 7199 that allowed it to 'verb it's own signal; the GA1 is as sweet a single-ended amp as there is ... this one is on eBay now:

I will definitely try yodeling when we get it put together. :lol:

You may want to sign up for lessons ... it's harder than it sounds.

A little Caps-A-Rama: #1 is a little daisy-chain action in a GA40LP like Mad Dog's (black over tweed). Tiewrap this one to that one, glue this one to the other (" .. I can't see it from my house ..."). #2 'flying' caps in a mid-50s Gibson GA20 - in the original pic, evidence behind the Mallory of a prior cap taking an electrolytic BM in the chassis.

#3 is Bill Ashton's 99J with 4 extra caps glued on with RVT foam. That's the original multi-section can cap underneath; the dropping resistors are still mounted on the hot posts ... the can got kicked down the road forcing somebody (Bill) to clean it all up and #4 is how St Leo of Fenderia solved it (mid-60s Super Reverb shown); put the caps in a doghouse on the tube deck. To replace; pull the chassis, open the lid, de-solder/re-solder, and put it back.

I might be tracing things out wrong, but if there is proper strain relief, I'd rather go straight from the new cord to the fuse rather than use an extra pin on the tube socket ... The little yellow 600V Cornell-Dublier is the "death cap" and it's gone for good with the new power cord, right?

- A 3-wire / #16 AWG cord is going to have a bigger circumference; you're going to need a new strain relief bushing and would be stuck hogging the existing hole out. A 3-wire / #18 AWG might be about the same size as the existing hole but offers less safety factor; thinking of you and the next owner (see remark about Bill Ashton's 99J above).
- I think this amp has one incoming wire going to the fuse block via an unused pin on the rectifier socket and then to the power switch and then to the transformer from the other side of the switch; your suggestion will work for one side of the incoming ... but we will need a place to tie the other incoming line to the other transformer lead ... the headaches are always in the details.
- Yes, the Cornell Dublier is the death cap. Once it's out, you can write someone's name on it and stick pins it it!

Three 20uf 600V electrolytic capacitors
Two 5pt center ground terminal strips
One 1k 10w wire wound resistor
One 22k 1w carbon resistor
One heavy duty three prong power cord

- Gonna need a couple of small bolts with nuts and lock washers. The hole in the ground foot on the wiring strip is a tiny bit small for #8 bolts ... you'll need bolts with no more than 1/8" dia shaft and say 1/2" long ... might stick out some but too short does no good here.

- 5' of #18AWG stranded in red, another 5' of green.
- Strain relief bushing for the new cord.
- two lug wiring strip with one foot ... I think this is where you need to tie the incoming service off; bring the lead from the fuse block to one lug, the other transformer lead to the other.

It leaves me wondering why the heck they didn't do it this way in '65. If they weren't gonna go for a three stage can in the Jets, this would have been easier to assemble in quantity and mount in the chassis with a certain amount of haste.

I think it's true that what was available could drive how things were done but mostly, it was a matter of least-cost. Clamping cardboard cylinder caps under cheesy metal straps assumed that the cardboard cylinders would be around 15 years later ... which they weren't. Considering than Ampeg had been using cans for sometime, their absence suggests cost avoidance was a language spoken there.

Most of this stuff was considered consumer goods - other than the Fenders, they weren't expected to last. It could be argued that by the mid-60s, kids wrecking amps or the amps blowing themselves apart were figured into out-years sales; there'd be a market because the stuff they were making wasn't going to last anyway. But nobody figured on the recession of the late '60s and the influx of transistor amps.

 

[capnjuan]

The first pic is a proposed fix to separate the incoming 110V AC power from the rectifier and its DC output. The idea is to mount a two-terminal strip on inside end-wall adjacent to the transformer; bring the 110V to it and terminate it there. One side will connect to one transformer input and the other will sneak around, hit the fuse clip, the power switch, and then to the other transformer input. The green/ground wire gets terminated under a transformer bolt with either a ring or spade terminal, crimped and soldered.

Below is a sketch to get around the messy wagon-wheel solder flop at the rectifier. There's an existing wiring strip in front of where the old caps were; it currently has the 22K/1W dropping resistor terminated as well as one leg of the 1K/10W resistor; there's also a ground terminal at one end.

The idea is to jumper from pin 8 (subject to confirmation) to the strip and mount the 1K/10W resistor there. Okay; we're moving the wagon wheel from pin 8 to here but now there are only 3 wires, not 4, to join. On the rectifier side of the 1K/10W, the center tap of the output transformer and its smoothing cap get connected. The other side of the 1K/10W supplies the next cap section, the 7591 screens, and the 22K/1W preamp dropping resistor.

The other side of the 22K/1W is terminated on the last cap section and the preamp power is taken from that junction. The caps are expected to be racked between two wiring strips. Their common ground wire can be left long enough to reach wherever it needs to go ... provided it's long, its destination doesn't matter. Littlesongs is probably going to use F&T caps which are nice and compact. If they are a little too wide to fit easily side by side, the center cap can be stacked on the other two and held in place by the strength of its own leads.