The PHILCO Phorum
37-670 No Sound - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: 37-670 No Sound (/showthread.php?tid=14198)

Pages: 1 2

RE: 37-670 No Sound - dfields69 - 03-12-2016

(03-12-2016, 02:16 AM)dfields69 Wrote:  No I did not check. Let me Pull it out over the next 2 dys and I'll post after checking all plate voltages.

What else could it be?

RE: 37-670 No Sound - Mondial - 03-12-2016

Could be a lot of things. Do you hear any hum if you put your ear to the speaker?

First I would check voltages on the audio tubes. You should hear noises in the speaker when you touch the voltmeter probe to the grids of the first audio or phase inverter 6J5 tubes. You should also hear noises if you touch the volume control connections with the control turned up.

If the audio stages check ok, then it might be something like an open coil or IF transformer in the radio frequency sections of the set.

RE: 37-670 No Sound - dfields69 - 03-23-2016

OK...I am back concerning the 37-670. I have replaced the interstage transformer and the filter choke. Both were bad. The radio now comes on, has a whirring sound through he speaker. You can tap on the 6J5's and hear it through the speaker. You can hear nice clear pock pocks when you turn the band switch. You can hear noise when touching the grid caps of the 6K7's and the 6A8. NO stations. UGH. Any ideas, anyone?

RE: 37-670 No Sound - morzh - 03-23-2016

Lots o'things.

I usually start with checking all coils for continuity. Every single one, from antenna xfmr to IF stage.
Oscillator could be not oscillating....

RE: 37-670 No Sound - Radioroslyn - 03-23-2016

Might be a bit easier to use a signal generator to go though the IF stage to check the IF, det, and audio. Do this by inserting a 470kc modulated signal down the grid cap of the 6A8.

You can listen for the LO at 470kc above the dial setting on the '670 with a transistor radio near the 6A8 tube.

If all that checks out ok hook your ant to the cap of the 6A8 mixer tube. Should hear stations if all is working except for the RF amp. Hook ant the the ant connection if rf amp is working you'll hear stations.

I feel for you bro I've got a 37-675 and it's a pita to work on. Mine has a bad rf amp coil or a bad band sw. Plays good if I hook the ant to the mixer cap, rf amp is dead. Hopefully it's something simple!!

Terry

RE: 37-670 No Sound - davemc - 03-24-2016

FYI on the driver transformer.  The actual measured ratio on my 37-670 was 2.71(CT) to 1(CT) measured at 400Hz at about 10 volts from my HP 200A audio oscillator.  The Hammond 124E would be a great match as it is 3(CT) to 1(CT). It would be connected backward. The dual secondaries would be connected in series aiding (CT in the middle) and used as the primary. The 15K(CT) primary would drive the 6F6 grids. The transformer is large, and can handle 5 watts. I have used it in several restorations and it works great. Another possibility is a Haldorson HVAT-2 universal driver transformer often seen on eBay.

My 37-670 had several broken hair thin wires in the RF front end, likely caused by capacitor replacement.  I finally removed the entire unit from the radio, pulled the band switch shaft, and removed each section for inspection and repairs. But I found that I had to reassemble the sections and install the band switch shaft in order to test the coils, since unused coils are shorted out in some of the sections!  This would mask any open coils.  What a piece of work!

37-670 Continued Woes - dfields69 - 03-31-2016

Hello again....I received much valuable assistance from you folks with the 37-670 I am working on. The interstage transformer needed to be replaced. Done. I discovered the filter choke was shot. Friend had exact replacement. Done. Recapped all bad resistors replaced all tubes good speaker field and output transformer/power tansformer are good. 10 of the coils in the RF subchassis are shot. Anyone out there got a junker with good coils or know how I could possibly proceed from here? Thanks.

RE: 37-670 No Sound - Ron Ramirez - 03-31-2016

I merged your new thread with your original one as starting multiple threads on the same subject is not allowed per Forum Rules.

Quote:II. Multiple threads on the same subject not allowed.

When you start a thread, please keep the discussion within the same thread.

Example: "Philco 90 broken"

After you've started that thread, please do not start another thread on "Philco 90 bad resistor" if it is the same Philco 90 being discussed in the original thread. Give others a chance to respond to your questions rather than asking them again in a new thread - please be patient.

These sort of threads will be immediately deleted, to keep clutter to a minimum.

Please cooperate with me in keeping one thread in the same place rather than scattering it around.

http://www.philcoradio.com/phorum/showthread.php?tid=4586

Now, with the legalities out of the way...

Do you plan to attend Kutztown? If so, send me a PM. I have one or two 37-670 parts chassis that need a new home.

RE: 37-670 No Sound - dfields69 - 03-31-2016

I cannot attend Kutztown due to starting a new job. If you have one of those parts chassis with good coils I'd like to pick it up and I'll gladly pay shipping to Roanoke Va. Sorry about the posting snafu. Still wet behind the ears on here. Thank you Ron!