Adcom GFA-585 Part 2 - Building the New Driver Boards

[@nohumbug8636]

Amazing detail. I have ADCOM equipment from the 1980’s, your video alerted me to capacitor leaks.

[@EdwardLehman]

Tins of good info, especially the info on Adcom units!

[@vinnievintage7725]

HOLY ****!! I am OUT with the installation of the Subistor's. Wow......., great information and explanation though Tony.

[@1959Berre]

I recently bought the wonderful soldering iron TS100 online in China. Costs about $50 and works like a charm. Very accurate temp control and a wide range of different tips, including a very fine one.

[@TheRadioShop]

Sure is coming along nice Tony. Good job on the board builds.

[@chrisvinicombe9947]

Great work so far , looking forward to part 3

[@exogarwinoputt4257]

OMG, Tony. I've had a GFA-555 for many years. It's a future BOAT ANCHOR!!

[@sirsuse]

You need to check it for damage. You may get lucky and get away with a recap and health check.

[@exogarwinoputt4257]

Just being a little sarcastic/ humorous. I'll see if it needs recappin'.

[@aug.jam.1]

Awesome work Tony, entertained me a lot, can´t wait for the next part

[@peterkunicki8183]

Delayed start is called de-thumping circuit which has been used since year zot in amps

[@Stelios.Posantzis]

4:53 Well, I've never heard of a stabistor before so I'm glad I watched this far. If I were just to have a look at the schematic, I'd just think it was a diode. I wish they would use a different symbol and have different a different casing and casing designations like that so that people can tell them apart from other regular components. Stabistors, fusible resistors, one wonders what else lies hidden in schematics/circuits that could mess up an unsuspecting repairer's day.... 12:15 That's the really tortuous way to go about it. Most people that are in the laptop motherboards' and mobile phones' repair business just use a stencil to apply the soldering paste and then apply heat with a hot air gun all over the component. I'm not sure how long these components can take the heat for (I'd guess they're made to take it) and how many times one can apply it to them before their properties are permanently altered or they get damaged but it seems to be a fairly standard method of soldering these. Then again, if you have the kind of dexterity and steady hands shown here, why not do it the traditional way.

[@circuitmonkey6653]

I just had to replace stabistors(that they don't make anymore in a Seeburg Amplifier. The replacement option from one of the Seeburg engineers was to, "place a couple signal diodes in series". It worked, but I remain skeptical. I think making a small board and using this surface mount would make sense for the next one.

[@phloodpants]

You're right to be skeptical. Certainly a couple 4148's will work, but the stabistors are chosen for a good reason. They have a much steeper I/V curve, and so provide much stronger regulation.

[@phloodpants]

You can also fabricate through hole stabistors, by soldering wire leads to the surface mount packages, and then pack putty epoxy around the whole package to keep the everything in alignment.

[@MrBrymstond]

It has a slow start circuit that usually has a relay that likes to go.

[@phloodpants]

More specifically, it's the 4.7R ceramic power resistor that fails open, which puts the full brunt of the stress on the relay, which then burns out. I replace the resistor with a metal-bodied 50W, as Tony shows in the video. The relay is super reliable as long as the resistor doesn't burn out.

[@DaveMcAnulty]

en.wikipedia.org/wiki/Stabistor for anyone else who had never heard of these before :)

[@robertcalkjr.8325]

Thanks Tony!

[@d.logic1]

where'd you get your eyeloop from?

[@1959Berre]

The automatic subtitles sometimes are just hilarious: "Put your ohm meter in diet mode..." (diode) (We don't want any fat component on the board, do we?)

[@rickyacasparyjr3638]

I have a California audio labs cl2500mca that needs repair would you be interested in looking at it?

[@DAVIDGREGORYKERR]

You know that guy 12voltvids well he always says work from the smallest to the largest would that not make sense, David Jones uses a SMD solder station with a microscope to let him see what he is doing.

[@digriz602]

Should of made a time-lapse of the board build.

[@1959Berre]

Why? Populating a PCB is boring.

[@rudigerhoppe5708]

Oh, I just saw it. The site owner's last name must be Hoppe, actually just like mine. So, it's a product of his brain. Says nothing about the first name, though. Sound's German to me.

[@phloodpants]

Hey Hoppe! Yeah it's German or possibly Dutch. My ancestors were immigrants to Milwaukee.

[@andershammer9307]

Surface mount devices ???? No thanks. I don't want to own any audio equipment with surface mounts. I once worked for a stereo store that sold these amps.

[@Thujaplicata1]

Me either.