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need help 45c restore - Printable Version

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need help 45c restore - Danny - 03-23-2018

Sent speaker out to be reconed. In the mean time I've replaced all paper and electrolytics.
Got the speaker back and installed. Powered up and all I have is a low volume hum. Checking 
voltages using pwr tfmr center tap to 8uf (62) Ive got 300vdc on 8uf (63) ive got 100vdc.
Doesn't seem correct to me. I've got about 35vdc on the plate of the 42 way low. Ohmed out choke
(59), Field coil (46), output transformer(44) and the voice coil (44) all good.
I have not restuffed bakelite blocks yet could that be the issue. 
Thanks in advance.

schematic http://philcoradio.com/phorum/attachment.php?aid=11978 

RE: need help 45c restore - morzh - 03-23-2018

Have you checked ALL the tubes?

RE: need help 45c restore - Danny - 03-23-2018

I've tested all tubes and replaced the 80 just for grins, no change.Both caps (62) and (63) are
installed neg to the pwr tfmr cntr tap and (58) neg to gnd. Just thought I'd throw that out
just to be sure I've installed them correctly. thanks for the response.

RE: need help 45c restore - Radioroslyn - 03-23-2018

>I have not restuffed bakelite blocks yet could that be the issue.

It very well could be. Could also be the caps in the tone control or a bad output transformer.

RE: need help 45c restore - 45philcodon - 03-23-2018

Danny,

I'm currently restoring a Philco Model 610 that has a very similar First audio/output schematic. A couple of things come to mind; one, your schematic appears to have a missing connection from the positive side of capacitor 63 to the junction of the 42 screen grid/output transformer/ field coil (white wire). Second, if that doesn't solve your problem, you need to determine where the 265 volts (300-35) is being dropped between the top of cap 62 and the 42 plate. Once we know that, we may be able to determine the problem.

Don

RE: need help 45c restore - 45philcodon - 03-23-2018

Danny,

My Model 610 measures as follows - top of your cap 62 = 336 volts
Drop across field coil = 68 volts
Drop across output transformer primary = 18 volts
42 plate = 250 volts

All measurements taken at zero volume.

Hope this helps

Don

RE: need help 45c restore - PhilcoPhan1936 - 03-23-2018

Here's a corrected schematic noting the missing connection:

[Image: https://farm5.staticflickr.com/4332/36057549620_9533a8b0b5_k.jpg]

RE: need help 45c restore - PhilcoPhan1936 - 03-23-2018

If it's been worked on previously, and they used the Rider's schematic, it's possible the connection was removed, according to the error in the schematic. I have a model 66 that had the same error, and a previous tech removed that connection. I found the wire still curled up under the chassis, and reconnected it, and bingo! Icon_thumbup

RE: need help 45c restore - Danny - 03-24-2018

The wire from cap to sg of 42 is in place.
top of cap (62) = 296
field coil = 201
output tfmr = 67
plate = 32
I'm going to start rebuilding bakelite blocks and tone control.
Got to much payola in it to push it aside. I'm going to keep plugging
away. Thanks for all the help and I'll keep everyone apprised of the
situation.

RE: need help 45c restore - Danny - 03-24-2018

Thanks for all the help guys....Turned out to be the tone control.
Replaced the 3 caps put it back together and it fired right up....
Again thanks for all the help. Now I'll tackle those bakelite blocks.

RE: need help 45c restore - Arran - 03-24-2018

Let me guess, shorted or very leaky caps in the tone control assembly, it's a good thing you didn't run it too long that way otherwise you may have been shopping for another power transformer. I found a similar problem in a Canadian RCA model A-20, the tone correction cap across the output transformer primary had a dead short, result was the same, dead radio, but since I didn't have a 1 Kv replacement I clipped it out just to confirm and the radio came to life. 
Regards
Arran