Asperger's & Autism Forum

Angular Chap

"You should also re-cap the entire board while you're in there" - every armchair electronics "expert" on the internet!

I have been poking around with the oscilloscope and some test tones. All the caps are fine. It turns out it was a combination of some oxidisation on the volume and the balance pots. But also some as yet undetermined dry joint somewhere. I couldn't track that one down. But a well placed thump to the case does the job!

Angular Chap

Ahh, percussive maintenance. Giving it a "dunt" as we say up here.

MildredHubble

It's a valid way of fixing things sometimes!

it looks like the loose connection/dry joint causes a reduction in volume across both channels but so far since getting a bit rough with it it's humming along without problems

It's a humble system, but it sounds lovely when it's cooperating, which to be fair is most of the time!

MildredHubble

Sorry if the lack of symmetry with my hifi drives anyone mad! I know I need to put the units in size order. The cassette deck is a recent addition so it just got dropped on top, but it's irking me a bit, I just don't want to upset the amp lol!

Angular Chap

Oh, that is a beauty though.

MildredHubble

Thanks! I like it

It definitely gets the job done

I'm very lucky to have one of these Trio amps. Modern ones just don't have the frequency response that amps from this era have!

Gerontius

If you're going to have old audio gear, you're going to have repairs--that's awesome you know how to fix this stuff; I don't know how to do electronics like that. Way cool.

MildredHubble

That's very true! I guess owning this sort of stuff, you learn a lot about repairing these things. One thing necessitates the other!

Gerontius

@MildredHubble I'm bad at electronics & still haven't fixed an Atwater-Kent AK-46 radio that I need to get working again. It used to work great but the power supply needs rebuilt. I have the schematic and it is a very simple set, but I'm still confused.
Wish I had your skills at this stuff.

MildredHubble

Perhaps you could swap out the damaged power supply? It may be easier said than done with some things. I'm not familiar with the Atwater-Kent AK-46. I may have to look it up

Gerontius

The power supply is repairable, but the Atwater Kent 46 was produced in 1929. It's one of the first AC-powered radio sets made. Unfortunately Atwater Kent fell victim to the Great Depression & went out of business in the mid-1930s. My set is in superb condition, right down to the cloth on the cords, and was playable until it began to smell odd when working.

MildredHubble

I looked up the radio but couldn't find a schematic. Only something that is probably similar. It may be because I looked at it on my phone but I can't make out a power supply. It's probably because old timey schematics aren't always very obvious in the way they are laid out. I think I can see a 4 tapped transformer so I'm wondering if that's essentially it for the PSU. I will have to look on a bigger screen.

MildredHubble

Ah! Odd smell, could be the insulation on the wiring if it's that old. It can just start liquidising. Also faulty caps can be rather pungent. Assuming the tubes are ok there's not much to old equipment really. If you work from one end of the power supply to the other replacing components as you go you will probably find the part that's faulty. Turn you can try and figure out what caused it to fail

Gerontius

I've got some excellent prints of original service documents, but what I don't have is a knack for building radios and tube audio gear. There's a reason I work more on phonographs & mechanical things like that. Attached a photo of the radio itself--homely thing it is; the 1930s ones in the attractive wooden cabinets look less like an oil-stove.

Gerontius

As for the smell--the condensers are "potted" in pitch and tar, & I actually got them out of there--they'd overheated the tar & I caught it before it burned up the radio. I do know there were some resistors (wire wrapped around straps of mica) and those were burned, and the condensers (somehow bundled-up looking like phyllo pastry, each about the size of a Pop-Tart) were shot too. It's a weird old radio.

MildredHubble

It looks excellent! I wish they made things like that these days!

If some resistors had burned up then it's likely something pulled to many amps through them. Tracking it down can be an issue when it's downstream. If cap failed short circuit this could have been the cause. But everything downstream could be the culprit.

MildredHubble

It's hard to know for sure without risking turning it on at some point and more things could get fried :-( But again if two wires smooshed together over time and shorted it may be more obvious. Though stuff like this is rather delicate and the wiring doesn't tend to welcome being moved around for fault finding :-(

Gerontius

This stuff is really cool. I like your receiver & amps a lot--bet it sounds a lot better!-- but is it ok if I eventually ask you about electricity?

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