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37-650 Success- and questions... - Printable Version

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37-650 Success- and questions... - Robbie Roberts - 01-04-2006

This is a "recap" of another posting I made, but I decided to break it out and give it its own subject thread... Thanks for the help!...

After an intensive recap, resistor replacement, and rewiring, my 37-650 is up an running...

Well, I've had her up and running for a couple hours now: while she is reasonably volumned, I am wondering if she may be a little quiet- and if so, how would I go about rectifying this? I found(before I added a rough wire antenna along the wall) that if I touched the top terminal of the 6A8G Det-Osc tube, the volume would pick up. With regard to the tubes, I replaced one of the two 6F6G tubes- and the other is a 6F6GT. And I seem to recall it(the GT) being a touch weak. Could this be the cause of lower than optimum volume?

All switches seem ok- I get nice tone change with the tone control.

AM and the first SW band seem fine- couldn't find anything on the top SW band, but I will try later in the day. With the antenna(just a long wire attached to the 1 terminal, and running between 6 and 8 feet high, about 30' long) in place, I get all sorts of stations- I found a Buffalo, NY station about 1520, which plays old stuff. I am outside of Philadelphia, so I know I'm catching a good signal.

I am pretty sure my Shadow Meter is not operating properly- I read through the information on Chuck's site, but I see no part which would operate as described in the way of a mgnetically induced flap- I am of the opinion it has been removed from the unit for some reason. All I get for display from it is a nice bar of light above the dial.

The dial lamp seems to be operating nicely- I like the way it back glows and has the well defined indicator line.

Anyway, any suggestions to how to inprove performance greatly appreciated.(All caps, bakelites, resistors, most wires, replaced or rebuilt)

Thanks!
Scott

- Jerry Huelsbeck - 01-04-2006

Hi Scott,
You have to have the antenna connected when playing. So with the antenna connected do you still have the low volume?

Your next step would be an alignment. Do you have a signal generator and vtvm ?

The shadow meter is most likely complete, dont know of any reason anyone would take the vane out. This also usually needs to have a decent antenna connected and properly aligned to get maximum deflection.

- Robbie Roberts - 01-04-2006

Yes- with the antenna connected, it still has reasonably low volume- I have one good, strong local(about 15 mile) signal(1210AM- used to be WCAU) which comes in moderately loud, but everything else requires almost full volume. I might take a look at my speaker transformers- it looks like someone was monkeying with them at some point.


I don't have any signal generator, etc. test equipment, but I am waiting on word from a guy in Delaware who does recaps, to see if he'd tune her up, now the leg work is done...

Scott

- Jerry Huelsbeck - 01-04-2006

I'd check your antenna coil, sounds like its open. I'd check that first before going on.

- Robbie Roberts - 01-05-2006

Ok- the low volume has gone to no sound- other than the slight hum letting me know it is alive. I had had low volume for most stations, save for the really close ones(such is AM) but had a full AM range to choose from- all over the east coast apparently! Bu my middle SW band had very little on it, and the top SW band I have yet to hear do anything. I am wondering if it is a speaker issue, an amplifier issue, a vol. control issue or what! All the tubes glow properly, and most were replaced with good used or new, if not up to par on the Precision 610 tester.

I haven't checked the antenna coil yet. Ideas?

Scott

- Chuck Schwark - 01-05-2006

Check all RF and OSC coils for continuity, per schematic and also the bandswitch - a dirty bandswitch with open contacts is all it takes too.

While you're at it, also check the IF transformers for continuity of primary and secondary windings.

- Robbie Roberts - 01-05-2006

Should I do the coil checks with everything as-is, or disconnect one end of each coil before checking continuity?(I dread having to do this, I have to pull the chassis again...lol but I'd have to to get it serviced anyway!)

Thanks!
Scott

- Robbie Roberts - 01-11-2006

First IF transformer checks out OK- and while I had it out, I replaced the shabby wiring I hadn't touched before- since I had to go in there anyway... Put it back together, and on to the 2nd IF transformer, next. Then I pull the sub-chassis to check all the coils... Icon_smile yay, fun Icon_razz

Robbie

Tube issue? - Robbie Roberts - 01-12-2006

I just ran a tube check on one of the two 6F6G tubes- actually, a 6F6GT that was in place of the original 6F6(The other had been replaced with an entirely different tube, and I put in a good used 6F6 from Radio daze)

Using a Precision Model 612 and proper data:

The 6F6GT tested good, except when the toggles were flipped: Number 7 glowed the short lamp, which it should have, but Number 8 also glowed the short lamp- a low glow, but definitely glowing when it should have been dark. Could this be my low/lost volume issue? I am currently in a deep stage re-teardown, and I'm about to take apart the subchassis... Although giving me an opportunity to correct a couple things I thought about doing but passed over, I really am not too hot for the idea. (This tube had been checked by a friend, and I suspect it may have been placed in the wrong pile- in good instead of bad: otherwwise I'd have replaced it)

Waiting for an answer- Thanks!
Scott

- Ron Ramirez - 01-12-2006

Replace that 6F6 with a known good one; that way there will be no question as to whether it is good or not.

Good luck with that RF unit.

- Robbie Roberts - 01-12-2006

Thanks, Ron, That's in the works now: I found the tube had been previously replaced with a 6V6GT... I looked at the numbers for both, and they seem similar, but not always... Is this an ok temporary/test measure, or should I just finish up, and wait for the new tube? When the 6V6GT was in place before, there had been a resistor added (330k ohm) between pin 5 of each of the two 6F6G sockets... Chuck believed that was probably just someone experimenting in the past, and I'm pretty sure he's right- I did not incorporate the added resistor when I rebuilt the chassis.

Scott