$5 Riviera Deluxe

[William]

Nice job, and thank you for the tip on balance control repair. I have a record player that does the same thing, loud left and right but soft in the middle. I may just try your suggestion. Of course I have no idea what resistance to use, mine is a PP tube unit and is a Magnavox.

Bill

[stbasil]

The choice of transistor was the result of Google AI providing some silicon types that were commonly used for germanium replacements, plus some other videos and articles that I found. I ordered an assortment from Amazon that had the 2N3906 along with 9 other types, (250 transistors for only $7!!!). I figured I'd be able to use one of those others if it didn't work out. I expected some trial and error, but it just worked. One guy on ARF said it would probably work in that circuit. But I know there are some circuits you would have to tweak the bias resistors, like the P-P output transistors, for instance.

I never found any reason for the oscillation, which is frustrating, but the caps fixed it without hurting anything. I do think the balance pot was just bad design, but maybe the oscillation was the result of aging components in a design that had marginal stability in the first place, not that I could have done any better back then!

Regarding the balance resistor, I just figured something in the range of 10 percent of the value of one side of the pot might work, and it did, but I had already tried adding 10K resistors on each end of the pot, which really made the oscillation much worse! So these solutions were not without many days of research plus trial and error all around the whole amp. I'm glad it's over (I hope).

[William]

Keeping my fingers crossed that it is over for you, at least with this project. And, thank you for the tip on adding the resistor to the balance pot. I need to work on my Maggie with the same issue, it now has woofer flutter in both channels no matter what input I use.

Bill

[stbasil]

Replaced the cartridge in the changer with the Pfanstiehl P-226D in Gary's kit, managed to get all the tiny fiddley pins soldered, had to widen the slots in the provided plastic mount, plus the little screws were longer than in the pictures of the instructions provided, but after all that it sounds good and tracks properly. So the original EV cart was indeed defective, I think the compliance was just shot, even though electrically it was OK. Set tracking at about 4 grams, a little higher than I wanted, but seems that what it needs. Changer detects sizes and drops records correctly, after adjusting the spindle pusher. The service manual has been very helpful!.

Unfortunately, the amp has started that oscillation issue again, not as bad as before, so I need to investigate that again. I had been using my test speakers for a while instead of the OEM ones; the oscillation reappeared when I reconnected them. Plus, there's some low frying sounds from time to time, probably coming from the two germaniums in the preamp that have not been replaced, so I'll try that.

Meanwhile, I've also started cleaning up the cabinet. Will discuss that later....

[stbasil]

The unit is missing it's Magnavox emblem, I think it may have looked like this (screenshot photo from a different model).

1000002699_edited.jpeg (88.77 KiB) Viewed 27 times

The holes in my unit look like this, the two holes on the left are 1" apart, the third one is 1 1/8" from the middle one.

I saw some joker on eBay offering two for $250.00, and they're plastic!

Anybody have any suggestions on where to find one?