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Discussion in 'Amp Central Station' started by HD28, Apr 4, 2021.
I wouldn't use ArmorAll on my ex-wive's cars.
And I hate my ex-wives!
I particularly do not like the look of any glossy looking treatment on a vintage amp. Ommv.
I see what you did there...
Reapplied the circuit label.
What is the sulfur looking corrosion or stuff? It doesn’t come off easy at all. I’m not too worried about it or the heat discolouration from the power tubes, just wondering.
Gonna start de-scratching the pots now.
The cosmetics on the amp were pristine when I bought it. I would wipe it down with a damp sponge on occasion, but never a detergent or a silicone like Armorall.
As far as the bias goes, I prefer adjusting without removing the chassis. I use bias probes. I once bought a 1986 Concert (Rivera era) 2 x 10. The power tubes were a Sovtek 5881 and Electro-Harmonix 6L6GT. The tech must have gone through a lot of trouble getting a pair that would deliver the right bias current. I rewired the bias pot to voltage adjust and put in a matched pair of TAD 6L6WGC-STR tubes, biased to 35 ma per tube and the amp sounded perfect. I gave the mismatched tubes to a friend that dabbled in amp maintenance.
If you're one that will pull the chassis and probe 400+ Volts with your multimeter, then simply adding a bias trim pot to the existing circuit is great. If you choose to avoid poking your probes into a hot circuit, then I recommend eliminating the bias balance in favor of bias voltage/current and a set of probes so you don't have to take the chassis out of the cab every time you replace power tubes.
My question about armorall was pointed at the grill cloth only. The plastic fibers will photo-degrade and off gas and will become brittle, so that when they get touched they will break and, well, that's not a good thing. I gave this one a vacuuming with a firm brush attachment to get rid of the dust. It’s still dirty but the dirt doesn’t bother me, I want to “preserve” the plastic cloth. If I can that is. I don’t know if armorall is only a marketing make things “shiny” product or if it really does make plastics and vinyls last longer...
I thought about cleaning up my SF Princeton since it looked so grubby compared to my PRRI, but thought better of it. Black tolex is a little unglued by the top front corners too, but it's an old amp--let it be old.
“Don’t be ashamed of your age” smiley face.
Please be patient with my noobism.
I wish to replace the filter caps under the doghouse. Which is what I think the 5 caps in the picture and the schematic snippet.
Please confirm if I think I know what I think I’m talking about...
Any advise on what and where to order new electronic components?
I like Uncle Dougs take on disguising the new caps in the old wrappers. Any thoughts are appreciated.
The 2 resistors between b-c-d read 4.53k ohms and 0.992 k ohms.
it's a lotta work for an amp that will never be a 55 tweed. ESPECIALLY if you're just gonna be starting with that sorta maintenance. You really really wouldn't want to get one of those installed backwards in its sleeve & not notice. tube amp depot, amplified parts, antique electronics are all pretty similar price-wise for f&t caps.
Wow, like new.
Death cap underneath 3-way ground switch. There is no continuity through death cap to chassis. Recall that the AB568 circuit does not show a 3-way switch, but this amp has one and was destined for export to Canada.
My dream amp - congrats!
imho, tolex should be reglued to prevent further degradation.
methinks spell checker did that for our amusement! Lol...
While shopping for cap kits I came across this.
The AB568 shows a 25 uF cap on leg 8 of V5.
The AA1069 shows a 5uF cap on leg 8 of V5.
This amp has a 5uF cap.
Unless there were any interim circuit designs between ab568 and aa1069, this amp is aa1069.
Can you suggest a source for the hardware and instructions for a bias voltage/current system?