73 Quad Reverb 100w. 'Restoration' into a head cab

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tubeswell
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73 Quad Reverb 100w. 'Restoration' into a head cab

Post by tubeswell »

Scored a 73 100W QR chassis/amp for very cheap. Trannies and Chassis date to late-ish October 1973.

Been gradually working on it over the last month. The insides have been badly mucked around with. The main (wax-impregnated) board has numerous band-aid components jumped off the board. I may yet re-do the main board with new board material, once I've tested it fully. Someone had installed a PPMIV at some stage in the past. The filter caps were still all original. I've since changed them, along with all the electrolytics. The OT Pr:Sec VAC checks out okay.

One of the 6L6 sockets had a blown 1R cathode resistor. I suspected something dodgy about this socket, so decided to replace all the 6L6 sockets and install new grid and screen resistors etc before test-firing. I reused the old wires and old tube clamps for mojo.

Someone has upped the bias supply with a small bucking transformer. It supplies the requisite DC but the workmanship is appalling. I will re-do this to with a 'stock' BF bias

The old lamp holder looked suspicious - someone had disconnected it and the contacts looked charred. I've fitted a new lamp holder and reconnected it.

The blown tube, reconfigured bias, and the disconnected Lamp point to previous power supply issues. Could be something dodgy may've happened with the PT. It checks out okay on a mains VAC test. However, the acid test for the PT will be with a new quad of 6L6s. I'll get around to that next week. Even if I have to replace the PT, it will have been a good score methinks

I spent today tolexing a DIY head cab for it. Going to run it with my 76 DSR cab (loaded with 2 x 15" orange-frame 'bels).
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drew
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by drew »

These were like a Twin Reverb but with four 12" speakers? What a back breaker.
tubeswell
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by tubeswell »

Yeah the 100W Super Six Reverb, 100W Twin Reverb, 100W Quad Reverb, 100 W Bassman Reverb, 100W Vibrasonic Reverb and 100W Dual Showman Reverb from the same era, all used basically the same amp, same chassis, same boards/parts, same trannies etc, but with different faceplates, and combinations of speakers/cab configurations. (The Super Six and Vibrasonic used different OTs, but the OT for all the others is the same AFAICT. I measured the VAC ratio on this and it gives 2k5 plate to plate with a 4R speaker load). The chassis I picked up was sans cab and speakers, so I decided it'd be easier to make a head cab out of it. I already have a mid-70s DSR cab with 2 x Orange-frame D130F all set up for 4R that I will run this with.
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jjman
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by jjman »

tubeswell wrote: Wed Nov 29, 2017 9:32 am Yeah the 100W Super Six Reverb, 100W Twin Reverb, 100W Quad Reverb, 100 W Bassman Reverb, 100W Vibrasonic Reverb and 100W Dual Showman Reverb from the same era, all used basically the same amp, same chassis, same boards/parts, same trannies etc, but with different faceplates, and combinations of speakers/cab configurations. ..........
Some pretty rare amps there. Intact Quads very rare. And the elusive Bassman Reverb...... Good luck finding one of those!
If it says "Vintage" on it, -it isn't.
tubeswell
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by tubeswell »

Cab's just about finished - awaiting SF grille fabric and fender 73 logo.
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Paulg
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by Paulg »

good call!
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M Fowler
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by M Fowler »

Good job Pete I have an old Bassman to recover.
tubeswell
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by tubeswell »

Thanks Mark. I must admit applying tolex isn't my favourite job. I tend to get a bit impatient with the gluing. Having a lino roller/brayer is essential.
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tubeswell
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by tubeswell »

Cosmetics on the new cab finished (bar a few replacement witchhats which I still have to find).

Still working on the guts
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Stratscratcher
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by Stratscratcher »

Looking good!
tubeswell
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by tubeswell »

Managed to knock the insides into some semblance of ballpark voltages yesterday. Is it too soon to say 'I sense a Eureka Moment'?
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tubeswell
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by tubeswell »

Finally chucked some output tubes in

Also some shots of the head with the cab - Spot the new witch-hats. :|
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drew
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by drew »

Seven meters! - OK, now you're just showing off :wink:
tubeswell
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by tubeswell »

I got the idea from Enzo over at MEF - plentiful and cheap junky meters available these days that are good enough for the job. So now when I'm taking voltages I clip them all up and take e'm all at once. Bonus is swapping clips around if you suspect a dodgy meter reading.
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tubeswell
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Re: 73 Quad Reverb 100w. 'Restoration' into a head cab

Post by tubeswell »

After some mucking around with a bunch of these tubes, I found 4 of them that are all within 1mA of each other, and its sounding pretty awesome. I'll debut gig it next weekend
Last edited by tubeswell on Sun Feb 25, 2018 6:19 pm, edited 1 time in total.
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