Look what appeared on my porch today. 610 B . I initially didn't want a shouldered model, but this one will do fine. Couldn't pass up one not worked over that was reasonably-priced.
The seller did as I requested and removed the speaker and mounted it to a piece of wood, ( Thanks to Kirk for that invaluable piece of info!!!)
In the seller's ad, the cabinet looked sorta rough for some reason, but now I think it was just light reflections, because it doesn't look bad at all in the flesh. I don't think I need to touch the cabinet too much ...maybe new grill cloth after I restore it electronically. ( I'll start another thread under electronic restoration when I dig into the back of it.) One of the knobs was replaced with some odd knob, but the seller included the original in an envelope on the shipping box. ( I've placed it back on the shaft for the pics here) It's missing it's small metal piece under the set screw, but I don't think that will be too difficult to correct.
I wanted a tombstone to juxtapose with the 89, and compare and contrast the two designs. I'm happy!
(This post was last modified: 09-19-2019, 08:12 PM by Jake Blake.)
Congratulations on that 610, Jake! Once you get it squared away electronically, you're going to love it. They are a pretty good set. I look forward to following your work on it.
I haven't actually worked on a 610 since I was a teenager, and that was a 37-610J, one of the consoles . Back then all it needed was new electrolytics, and a tube, and it was good to go. I do have a lot of experience with the 37-61, 37-630, and 48-482 though, as well as other makes. I'll give you what advice I can when you ask, but Ron and the others here know even more than I do. They'll be of even greater help, I'm sure. I do look forward to watching your progress with it.
"Back then all it needed was new electrolytics, . . . "
Thanks Mike.
I indicated earlier this 610 was unmolested, but that was more a commentary on it's cabinet than it's electronics. I knew it had already had a filter change . They still have to go again...looks like at least one of them is leaking and I don't think they're the correct values. I'd really like to get the poor 39-6 C I going before I tackle this dude.
Good luck, Jake. By the way, don't let some folks here fool you about electrolytics. You CAN go OVER in capacity by as much as double, I have with no ill effects, but up to 50% is more like it, say, using a 30MFD for a 20MFD, or a 22MFD for a 20MFD, but only if you have to. I always go OVER in voltage, using 600 volt continuous rating, even if the original was 450 volt. NEVER go lower in either capacity or voltage rating on filter condensers. Also, be careful about the polarity. One of the originals has an insulating fiber around the can, with a tab connection that isolates the can. It filters the negative bias voltages, and is important to hook up correctly.
Looking at the schematic for your radio, the plain 610, I think the oddball is #56, an 8 MFD condenser. You could use 10 MFD for all of these 8 MFD if they are easier to get. Get them with a 600 VDC working voltage.
The Motorola 51x17 got 24s to replace 20s, . . . . I believed that was close enough also, although it has stopped playing properly in the last few days. One might wonder if the 25% extra capacitance taxed the rectifier, but I am still without a way of testing tubes here to find out which one has bit the dust. We'll see....eventually.
I'll get the 600 volt caps when I start re-capping the 610. I guess I'll test the power transformer before purchasing anything though. I hope I don't have another disappointment there, like with the 39-6. I'm still trying to get an answer on whether anyone believes a radio will still operate with 1/2 a secondary open.
I noticed that insulator on the one cap in the 39-6 also, and am slowly picking up on that negative bias-thing. It's an irritating anomaly of circuity design in these Philcos to me,
( among numerous others), but I guess that's just the way Philco decided to do that, instead of with another secondary voltage and rectifier like I've seen in other circuits. I know how important negative bias is,.... I've seen output tube's plates light up like filaments without it.
(This post was last modified: 09-22-2019, 05:54 AM by Jake Blake.)
Jake, I've seen rectifier plates glow red when the electrolytics have gone bad! I doubt that extra capacity on the filter condensers was a problem with the 51x17. It would cause slight extra current through the transformer and rectifier while they were charging up at the beginning, only one or two cycles, a fraction of a second, but after that be normal, and actually give better filtration to the DC. I'd look for another problem there. As for the isolated condenser, it is really pretty clever. What the circuit design does is put one side of the rectified DC negative compared to chassis, and the other positive compared to chassis. It saves needing a double power supply. Much later designs use a cathode resistor with a bypass condenser to cause the grid to bias negative with regard to the cathode and smooth out the bias voltage by bypassing any signal from the voltage, but this is not as good, and does not give as steady a bias. Nope, those old designers knew what they were doing when it comes to tubes. My T8-18 RCA uses a similar set up to the Philcos to produce the negative bias and positive plate voltages. That's why it has the two candohm resistors. If you have a bad power transformer, I wish you luck. You can get them rewound and rebuilt. I'm not sure where, never have had to have it done, but I'm sure someone here knows where. Antique Electronic Supply also carries quite a few replacement transformers, one of which might work.
Heyboer Transformers Inc. They are in Grand Haven, MI, about 20 miles from where I live. I have no idea of the cost, but they can do it. Or...rewind it yourself! Tedious, but doable.
"I doubt that extra capacity on the filter condensers was a problem with the 51x17."
Yes Mike,...I wasn't necessarily suggesting the new caps were the reason a tube now appears to have gone bad in the Motorola, ( it worked fine for weeks). They're probably just getting old. I'm wondering if some of them are originals. I'm just without a way to find out which one. It may very well not even be the rectifier that's bad.
"Much later designs use a cathode resistor with a bypass condenser to cause the grid to bias negative, . . . "
it will take me a while to wrap my head around what you say here. I'm trying!
" If you have a bad power transformer, . . . "
I just wish I knew whenit went bad..... before I bought the 39-6 ( even though it worked a little when I got it), or afterwards, when I re-insulated the leads and somehow damaged it working on it. I guess that should be taken up in another thread.
I guess that should be taken up in another thread.
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