[Guest]

Hi all, I'm new to this forum I just found it while looking for some info on repairing a Philco 37-61. Now on to my question, I have been working on this radio for some time and can not get it to perform like it should. It will not bring in stations very well down below 800kc, but if I attach the antenna to the grid of the first tube 6a8g it will work much better. I have tried to align it over and over without any improvement. also the trimmer cap for the antenna transformer must be backed out all the way for best results. I have tested the antenna transformer for opens etc.. and it is ok. By hooking up the antenna to the grid of the 6a8g, what i'm doing is bypassing the antenna transformer, why would the radio work better when I bypass a part? I have been able to adjust the osc. so that a station that broadcasts on 680 comes in at 750kc and it comes in much better but when I "chase" it down the dial by adjusting the osc. alittle then retuning it back in-readjust the osc-retune the staition-adjust the osc-retune etc... by the time Iget it down close to 680 on the dial it will be so weak it hardly comes in.
On other sites someone asked if my signal generator was any good and said I should test it aganist a digital radio, so I did and found that it's output was very broad, allover the band, so I tried another signal generator. not much inprovment if any.
Thanks for any help
Tom
Maryland

[exray]

I'd suggest a good bandswitch cleaning, then attempt the alignment again. Inspect the switch to make sure there are no broken tabs or the like. Your description of getting 680 moved to the right spot on the dial and the signal weakening is an indication that there is still a problem somewhere between the antenna and the grid. If the antenna coil checks out then the switch is the only thing left.

GL,
Bill

[Guest]

Thanks, what I'll do is with a jumper wire I'll bypass the bandswitch and let you know
thanks again
Tom

[exray]

I just noticed your thread on ARF. Just to add something in case it hasn't become obvious yet...I think that model may use some of the dual trimmers...screwdriver adjust in the center and outer nut adjustment for the other trimmer.

[Guest]

Bill, I bypassed ALL connections on the rf side of the bandswitch--no better. I have tried a new 6a8g tube no better.
Yes, I see how this radio uses the two trimmers, the outter nut for the lower area of the band and the inner screw for the upper. If you saw the other post, you read the idea about installing a .01 cap before the rf section of the tuner cap. Well I just did that and guess what, that did not even move the place on the dial where the 680 station comes in. This morning that staition does come in stronger that at night (they may reduce power at night) but other stations on the low end of the dial come in louder also. this is with the added .o1 cap installed or not. The radio is still not right as I can touch the grid of 6a8g tube and it will come in louder, I do not get this effect at the upper end of the dial.


Tom

[exray]

Hmmm. You said you ohmmed out the coil already. Did you do so measuring directly from the antenna terminals and directly from the grid of the tube for the other side? Check also on the megohms scale for leakage to ground.

Any chance the antenna section of the tuning cap is shorting as you rotate it lower in the band?

[Guest]

I checked for opens both ways as I got further into it but I did not chect to ground. I have the schematic and it shows 6 ohms on secondary side and a center taped primary with both at .7 ohms for a total of 1.4 ohms this all tested ok. give me 5 min and I will check the coils to ground
Thanks

[Guest]

Checked to ground, had to unsolder a wire on the secondary and unhook the "link" on the antenna connection "panel" but all tested ok. What about the AVC? I think that is the wire that I had to unsolder, could the avc do ant thing to just one end of the dial?
Tom

[Guest]

Bill, I must start to get ready to eat (1hour drive) so I want to thank you for the help and if you make another post I will get back to you late tonight or tomorrow. Thanks again
Tom

[exray]

Nope. It has to be between the antenna and grid. Did the variable cap antenna section check out ok?

You've got me curious now. I have a 37-61 that WAS working. A friend in the UK needed an antenna coil so I sent him mine. He sent me his old one and I repaired it and stuck it somewhere in the shack for later installation. Apparently I have been burglarised since the coil is now nowhere to be found I figured I'd have to make up a toroid coil or something. Did that once on a similar Philco and it worked out ok.

At any rate, your problem is still waiting to be found and I'm fresh out of ideas. I read all the comments about the IF alignment and I take it you have that under control. If you were 20 or 30 kc off on the IF alignment you could experience similar symptoms since that would spoil the tracking. Antenna shouldn't make a difference but just need to ask, you're not attempting to use a directly connected loop or anything like that?

-Bill

[Guest]

Bill, the rf section of the tuner did check out ok, sorry I did not get back on that one. I checked it with a meter and it is not shorted and it is 360mmf fully closed. On the antenna, I have been swaping between a long wire strung up in the rafters and a wire that goes around the rear inside of the framing of the radio,it is a console model. The wire up in the rafters performs better but not much. Now this is downstairs and the rafters are the floor of the ground floor, about 2 feet above ground level. Once, I took the radio upstairs to see if that would help-no better. On the topic of antennas, on the schematic it says that it should have a "high-efficiency" aerial and that the "transmission lines" go to terminals 1&2. Do you have any idea what that is?
Tom

[exray]

That would be one of their All-wave antennas that are like a multi-band dipole. Simply an option that they sold. Not really at issue here.

I really got my story bungled on the above post. I pulled out my 37-60 a while ago. Thats the one in which I used a ferrite toroid to replace a missing OSC coil. The 60 and 61 are quite similar, however, at least for BCB. I poked around looking to see what additional clues I could come up with and I've run out of ideas. I cannot help but think that the coil somehow is the culprit here.

Backtracking on an earlier path...you mentioned having to take the AVC loose when doing the coil-to-ground test. I was reviewing that and see that you would have measured about 2 Megs to ground. Is that pretty much the ballpark range of what you saw with the AVC connected? Something else I wish I had thought to check while I had my chassis out of the cabinet and thats the method of grounding the subchassis to the main chassis. What I'm getting at here is making sure that cap #4 finds a good rf ground.

How well does the shortwave work? Do you notice any dropoff on the low end of that band?

[wonderwrench]

Hi all, I'm new to this forum I just found it while looking for some info on repairing a Philco 37-61. Now on to my question, I have been working on this radio for some time and can not get it to perform like it should. It will not bring in stations very well down below 800kc, but if I attach the antenna to the grid of the first tube 6a8g it will work much better. I have tried to align it over and over without any improvement. also the trimmer cap for the antenna transformer must be backed out all the way for best results. I have tested the antenna transformer for opens etc.. and it is ok. By hooking up the antenna to the grid of the 6a8g, what i'm doing is bypassing the antenna transformer, why would the radio work better when I bypass a part? I have been able to adjust the osc. so that a station that broadcasts on 680 comes in at 750kc and it comes in much better but when I "chase" it down the dial by adjusting the osc. alittle then retuning it back in-readjust the osc-retune the staition-adjust the osc-retune etc... by the time Iget it down close to 680 on the dial it will be so weak it hardly comes in.
On other sites someone asked if my signal generator was any good and said I should test it aganist a digital radio, so I did and found that it's output was very broad, allover the band, so I tried another signal generator. not much inprovment if any.
Thanks for any help
Tom
Maryland

My 620 had a similar problem. I never did find the actual cause though the trimmers may have degraded over time. I did find that changing the dial scale positioning allowed the trimmers to work as designed. This also corrected dial scale error and overall tracking of the radio. I'd try aligning the radio like you did when 680 came in at 750 then move the dial scale so 680 comes in at 680 then see how the radio performs. You may have to play with moving the dial scale slightly one way or another to get the best tracking. I ended up with the dial scale approx 1/4 inch below the cal line on the bottom of the dial scale.

[exray]

Very good point, Bill (wonderwrench). I believe Brian can tell us some stories about getting the dial aligned for best performance.

Curiosity got the best of me so I pulled my 37-60 out again. I see the .05 cap is well grounded right to the frame of the tuning cap. Not much room for error there. I also measured from my grid cap to chassis and saw the 2.0 Megs I suspected. That would confirm no shorts to ground in the coil/tuning assembly.

I hate to mention this because its dumb but I once found a radio where the grid cap wire had been connected to the wrong section of the tuning cap by a previous restorer. There had been a gimmick between the two sections on top of the tuning cap. The fellow had replaced it with a straight wire. (the tube label inside the cabinet actually had a line drawn there in the pictorial layout diagram) Using the same logic he reattached the grid wire to the terminal which happened to be the wrong one. That radio actually played a little bit - although I'm not sure how. I found the straight-wired gimmick easy enough but I didn't realize that the grid was incorrectly connected.

It goes to the rear section in the Philco.

[Guest]

bill and bill, I did get the 2 meg from the grid to ground, in fact it was 2.03 meg. the tuning cap and the .05 are all good ground, as I checked this early on in this, at first I could not see where the sub-chassis was grounded so I ran a good ground to the main chassis. Then later on I found how it is grounded. Thats the way it goes.. the thing about the grid lead not going to the correct section of the tuning cap-it is connected to the same side as the correct wire that comes from the bandswitch, I guess both could be wrong. someone asked about the SW band, well it works fine as far as I know, don't know if they come in on the correct place on the dial but it aligned fine the first time(I should redo it) and I get good responce at the low end of the dial. If the grid wire was wrong I think SW would suffer, but I must say that the SW band works as good or better than other radios that I have, even with the short antenna and downstairs.

I think that if I can't find anything else I may just try to move the dial to the place that works the best.
Thanks for the help
Tom