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38-116 Code 121 Powering Up Help - Printable Version

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RE: 38-116 Code 121 Powering Up Help - AVSorrell - 07-30-2017

Hi Terry - good point. I added an additional safety cap as the schematic called for and as you suggest. I don't get 120 vac across the primaries but it is close 105 vac once she is warmed up.

RE: 38-116 Code 121 Powering Up Help - morzh - 07-30-2017

What is that CL-90 thingy it goes through?
Also have you cleaned the power switch and how much is dropped across it?

RE: 38-116 Code 121 Powering Up Help - Radioroslyn - 07-30-2017

Mike, The CL90 is one of those new fangled xsistor thingies that slowly applies the ac line voltage as it heats. I think it's 90sec to get to full on.

Put a jumper across it or loose it.

RE: 38-116 Code 121 Powering Up Help - morzh - 07-30-2017

Useless for these radios anyway, but if you want to keep it first see how much it drops, and also see how much the switch drops.

RE: 38-116 Code 121 Powering Up Help - AVSorrell - 07-31-2017

Okay - I bypassed the CL-90 and am up to 110 vac across the primaries and at the switch - but still no reception across the bands.

RE: 38-116 Code 121 Powering Up Help - morzh - 07-31-2017

Getting 105V across the primaries would not be a reason not to get reception. I thought you were just interested why you have lower voltage.
I don't want to replace Terry as the main adviser in this topic, so I just give you general pointers:

1. Check that your audio is operational (you know, touch some grids, hear some buzz).
2. If you have a tracer, go see where the signal stops when you inject it in the antenna.
3. If not, then just start checking RF coils' continuity.
4. I also noticed that when you say "the tubes have been checked" and then Terry guided you some further, some of the checked tubes turned out not to be good.
5. Use generator, see where the signal stops.

RE: 38-116 Code 121 Powering Up Help - AVSorrell - 07-31-2017

morzh - Thank you - Terry you too have been a super big help as I troubleshoot to find my issue. Before I powered anything up I tested all tubes and the only bad ones were the rectifier 5X4 and a 6J5. But in the course of my repair work I think I shorted one the 6L6s so I just got two replacement ones. I have not retested all the tubes since I began powering things up so I shuld probably try them all again.
My audio is operational as I hear buzz when i touch the grids. I do not have a tracer, but I do have a signal generator and and can use my output meter. I have a signal counter to make sure the signal generator is aligned correctly. I guess after I check the tubes again, I will need to find the signal stops.

Thanks for all the pointers guys - it is very helpful and keeps me from feeling this project is over my head!!

RE: 38-116 Code 121 Powering Up Help - Radioroslyn - 07-31-2017

> keeps me from feeling this project is over my head!! 

Well it's not your average 5tube ac/dc model!!!
I would start by using your sg set up to generate a 470kc signal w/modulation. Go around to the grid caps of the IF amps (6K7's) and see if it will pass a signal. Have the fidelity/tone control tuned to treble this will give you the widest IF bandpass. Doesn't matter where the main tuning is set.
When troubleshoot ing the RF deck an octal tube extender can be a very handy thing to have. It allows you to access the tube's connections from the top of the chassis rather than trying to dig around on the under side.
[Image: http://k4che.com/tube%20extenders/misc%20extenders%20250.jpg]
You can make one if you have an old tube base and a socket.

RE: 38-116 Code 121 Powering Up Help - morzh - 07-31-2017

37/38-116 are in fact pretty intimidating even for an experienced restorer, let alone for others. And the 38-690 I am dealing with right now is even more so. Although the 116 is harder to recap due to the way its RF chassis is made.
And then some folks like Russ restore Z-1000 with full wire-stripping, re-plating etc. Not to mention the cabinet work that is downright spiritual experience, like climbing Mount Everest.
So.....this too shall pass, just don't let the scope of the project intimidate you, concentrate on the task at hand. Works for me. Icon_smile

RE: 38-116 Code 121 Powering Up Help - Steve Davis - 07-31-2017

Andy, you should check to see if your oscillator is working. Tune your 38-116 to about 1000kc and tune another radio to about 1470. Rock the tuning dial on either radio to see if you can hear the oscillator of the 38-116.

Steve

RE: 38-116 Code 121 Powering Up Help - AVSorrell - 08-01-2017

Thanks for the ideas! Good news is that I tuned my signal generator to 470kc and connected it to the grid caps of 1st and 2nd IFs 6K7s and heard a signal loud and clear from the speaker. I also heard a signal on the 6k7 RF grid cap and one on the 6L7 mixer on the rf deck. I did not hear a signal on any other grid caps. I tuned my 38-116 to 1000 kc and another radio to 1470 kc and rocked the dial and did not hear anything from my 38-116. I have some bad tubes I can make a extender as I trouble shoot the rf section - good idea!!

RE: 38-116 Code 121 Powering Up Help - Radioroslyn - 08-01-2017

Good!  Next step would be using your generator connected to the grid cap of the 6L7 and the 6K7 w/ the generator set at the same frequency as the radio's dial. Listen for the signal and see if they track ( if you retune the generator up or down a bit can you retune the receiver and pick it you again at the appropriate frequency? If you can't receive any signals at the dial frequency then we will have a look at the local oscillator.

As Steve mention you can listen for it @ 470kc above the dial setting of the Philco. If you have a little shirt pocket transistor radio hold it near the 6A8 tube (assuming it's glass not metal, philco was big on GT's) and tune it around the prescribed frequency and see if you can hear a loud hiss in the transistor set. If the LO isn't working you'll need a tube extender to make like easier when doing the troubleshooting on this circuit. If you another 6A8 I'd try it in the set.

RE: 38-116 Code 121 Powering Up Help - AVSorrell - 08-05-2017

Hey guys - I have checked all the tubes and found some issues with a few - but replaced all with good ones now. I still hear the signal generator on the 1st and 2nd IF tubes but nothing when connected to the 6L7 and 6K7 on the RF deck w/ the generator set at the same frequency as the radio's dial. Ugh. so how is the local oscillator troubleshot?

RE: 38-116 Code 121 Powering Up Help - Radioroslyn - 08-05-2017

here's a couple of simple things to check. Connect your ohm meter to the stator of the tuning cap (osc section) and the chassis. With the cap completely open note the resistance. Slowly close the cap and watch the meter for any fluctuation in resistance (lower rather than higher). This would be indicative of a short between the stator and rotor plates. From what I can see there isn't any coils connected across the tuning cap so I think w/the cap open your going to see a pretty high resistance to start with.

Is the band switch cln??

Use your tube extender and measure the pin voltages on the 6A8 to see if they are close. Just for grins check the osc w/the 6N7 removed.

If you want a fun toy I have a spare programmable frequency counter. This can be easily connected to the osc output and can tell you it's exact frequency. It also can be set  up to display the exact frequency that the set is receiving (digital dial) which can be handy for doing the osc alignment. You can order from China but in takes abt 3 weeks to get here. If interested pm me.

RE: 38-116 Code 121 Powering Up Help - AVSorrell - 08-06-2017

Hi Terry!

Okay with tubes I know that are good, I took measurements of all 15 tubes pins, the interstage transformer pins, neutral and hot of the AC line cord, filter caps (141 & 142), electro caps (140 and 140a and 80a and 80b) choke 136 and choke 138 and the resistor junction of 134 and 135.  here goes.

-- where the line cord enters the chassis I got 110 vac across the hot and neutral.
-- across the power transformer primaries I have 107 vac
-- for the power filter caps 141 and 142 I get 333 vdc positive to negative (should be 385) and I get 281 vdc positive to ground.
-- for electro caps 140a where the positive goes to ground and the negative to the negative of the filter caps, i have -48 vdc (should be -50 vdc I think)
-- for 140 I have 270 vdc
-- for electro cap 80: I have 256 vdc, 80a: 236 vdc, 80b: 85 vdc
-- for choke 136 I have 283 vdc for the pin closest to the front and 270 vdc for the lower one.
-- for choke 138 I have 236 vdc for the black wire and 245 vdc for the white wire
-- at the junctions of resistors 134 and 135 I have -21 vdc
for the interstage transformer I have: pins 1 through 4: -20 vdc pin 5: 236 vdc pin 6: 231 vdc

I f I do not list a pin it read zero. My largest discrepancies are on my oscillator (6A8G) and oscillator control (6N7G) tubes.

Rectifier Tube 5X4G:
across pins 1 and 2 (filaments): 4.85 vac
chassis to plate on pin 4: 341 vac
chassis to plate on pin 6: 341 vac

Output tube #1 6L6G (closest to side):
pin 2: 6 vac (should be 6.3 vac)
pin 3 262 vdc (should be 290 vdc)
pin 4: 267 vdc (should be 300 vdc)
pin 5: -21 vdc (shuold be -20 vdc)

Output tube #2 6L6G:
pin 2: 6 vac (should be 6.3 vac)
pin 3 263 vdc (should be 290 vdc)
pin 4: 268 vdc (should be 300 vdc)
pin 5: -21 vdc (should be -20 vdc)

6J5G Driver tube:
pin 3 230 vdc (should be 260 vdc)
pin 5: -6.8 vdc (not sure what this should be)
pin 7: 6 vac (should be 6.3 vac)

6K7G RF Tube (on RF subchassis):
pin 2: 6.1 vac (should be 6.3 vac)
pin 3 237 vdc (should be 250 vdc)
pin 4: 85 vdc (should be 90 vdc)
pin 5: 2 vdc (should be -3.5 vdc)

6L6G Mixer Tube (on RF subchassis):
pin 3 225 vdc (should be 250 vdc)
pin 4: 90 vdc (should be 90 vdc)
pin 5: 2 vdc (should be -3.5 vdc)
pin 7: 6.1 vac (should be 6.3 vac)

6A8G Osc Tube (on RF subchassis):
pin 3 260 vdc (should be 180 vdc)
pin 4: 260 vdc (should be 110 vdc)
pin 5: 260 vdc (should be 125 vdc)
pin 7: 6.1 vac (should be 6.3 vac)

6N7G Osc Control Tube (on RF subchassis):
pin 3 275 vdc (should be 225 vdc)
pin 4: -3 vdc (not sure what it should be)
pin 5: -3 vdc (not sure what it should be)
pin 6: 275 vdc (should be 225 vdc)
pin 7: 6.1 vac (should be 6.3 vac)

6K7G 1st IF Tube:
pin 3 231 vdc (should be 250 vdc)
pin 4: 85 vdc (should be 90 vdc)
pin 5: -2.6 vdc (should be -3.5 vdc)
pin 7: 6.1 vac (should be 6.3 vac)

6K7G 2nd IF Tube:
pin 3 226 vdc (should be 250 vdc)
pin 4: 85 vdc (should be 90 vdc)
pin 5: -2.6 vdc (should be -3.5 vdc)
pin 7: 6.1 vac (should be 6.3 vac)

6J5G AVC Tube:
pin 5: -5.3 vdc (not sure what it should be)
pin 7: 6.1 vac (should be 6.3 vac)

6K7G 2nd detector Tube:
pin 3: 34 vdc (should be 40 vdc)
pin 4: 18 vdc (should be 15 vdc)
pin 5: 18 vdc (should be 15 vdc)
pin 7: 6.1 vac (should be 6.3 vac)

6J5G Disc. Tube:
pin 3: -0.6 vdc (not sure what it should be)
pin 5: -9.4 vdc (not sure what it should be)
pin 7: 6.1 vac (should be 6.3 vac)
pin 8: -0.6 vdc (not sure what it should be)

6J5G Disc. Tube:
pin 3: -5 vdc (not sure what it should be)
pin 5: -18 vdc (not sure what it should be)
pin 7: 6.1 vac (should be 6.3 vac)

6R7G 1st Audio Tube:
pin 3 69 vdc (should be 70 vdc)
pin 7: 6.1 vac (should be 6.3 vac)