Hi-Fi Guidance

[keithb7]

Enzo, what is up with the labelling on those diodes, seems backwards to me?

My basic understanding is that the arrow points toward cathode (-) on the diode.

[Enzo]

To me the triangle (arrow) looks like an A, so ANODE, the bar is cathode. That is the flow of "conventional current", not electron flow.

If I send AC into the anode, I expect positive DC on the cathode side.

I expect the square symbol terminal on the two leg cap to be positive.

I am just guessing, but from the photos, I think I am seeing this as a single supply power amp, the large two leg cap being for that. Then there are two smaller 1-leg can caps next to it, with the 0.5 ohm resistors. I see those as output speaker caps for the two channels. Anyone else get that impression?


I cannot see it well, but it LOOKS to me like the bare wire lead from the positive leg of the 2-leg cap might go to a ground lug? Meaning this amp is running on a negative supply, like maybe PNP types, likely germanium?

[gbarron]

Your explanation of the 3 caps makes sense, the large for the power supply and the 2 smaller for the speaker channels. There is a fourth large cap as well but I believe it may be for the cassette portion of the unit.

The bare wire is coming from a shielded lead, the inner wire of that lead runs to a circuit board. The black wire running from the same post as the bare wire runs to a chassis ground.

[gbarron]

It's worth a try to check with justradios.
They say 'antiques' but seem to have stuff right into the 70's :
Canadian Antique Radios Schematics Diagrams Service - JustRadios

Thanks for the lead, I will shoot them an e-mail.

[g1]

I cannot see it well, but it LOOKS to me like the bare wire lead from the positive leg of the 2-leg cap might go to a ground lug? Meaning this amp is running on a negative supply,

Ok, I only thought the diode labelling appeared reversed because I expected a positive power supply.
From the way the diodes are connected, yes, it must be a negative supply voltage at the triangle lug, with the square lug grounded.

[keithb7]

Well folks, my brother and I finally hooked up this weekend. I had changed out all the e-caps over the summer and the circuit sat until now. The radio sounds excellent. We have AM/FM, Phono working good. The cassette player is acting up, but wired in via RCA jacks. So we hooked up RCA to headphone adaptor and hooked up an ipod. Sounds amazing. We have 1 bad pot that is crackling and cutting out. This is the volume pot. I assume, the most used pot in the console. I see that it is a double pot. There are markings on the back that is reads "10 + 37K" and "90091 C7". A pic of this pot is below here. Any help in ID'ing a proper replacement pot would be appreciated. I have done some google searches with no luck yet narrowing in.
There are two legs on each pot that solder to a circuit board. I am doubtful that we will find an exact fit, however I am pretty comfortable wiring up jumper wires instead, from the pot to the board.

We had a great time working on this together. It has been quite rewarding. We are quite impressed how great this console sounds. It has woofer, mid and tweeter speakers, in stereo. I must say I am jealous. I'd love have it in my man-cave.
Thanks in advance. - Keith

[keithb7]

More views of the pots. One of them is the volume here:

[nickb]

Good to hear that it all worked out

I didn't follow this when you first posted, but if I had I would have said that the definitive way to test the capacitor polarity on a working system is to use your (DCV) meter. A lot easier than all the speculation.

[keithb7]

Here it is: