The Stovebolt Site Forums The Shop Area The Electrical Bay The Radio Bench '54 alignment

I'm an old radio repairman, so quite familiar with old radios. Problem: radio will not align per Sams manual. L5 seems to be low on inductance but ohms correctly. Tuning core appears to be ok, C5 checks good with captester. IF aligned at 262khz and new 6BE6. By increasing the value of C5 from 180 pf to 530pf I can get all of the alignment to work . . . but I'm not thoroughly satisfied with the operation of the radio and I know something is not right. Got any ideas??? Don

Hi Don,
do you have continuity on both side of L5? Also, I wonder if there is a problem with the trimmer assembly, A5?

I have another thought about this. Maybe you have a broken slug?

Fred

Fred,

I appreciate that you got with me on this so fast, I am waking up at night thinking about it.

L5 prim/1.2 and sec/4.8; with trimmer discon from L5 meas min/120 and max/180. I completely disassembled the tuning assembly and carefully inspected, all three tuning slugs are solid, no ships or cracks. The die cast can for the three coils has ferrite sleeves in the can for L2 and L4, none for L5. Is this normal? If there should be a sleeve for L5, there is no evidence that there ever was one. No sleeve would make the inductance low. I don't see anything else that could be a problem. This has me stumpped.

Don

Don,
I may be looking st the wrong diagram but on mine, C5 is associated with L4 which I believe controls the oscillator. L5 on my diagram is an IF transformer. My diagram is for model 986669 which may be for the car version.

Fred

Fred,

My Sams is for the truck # 986771, the osc circ is C6-L5 on this diagram. What do you think of the lack of a ferrite sleeve?

Don

Thanks for the data sheets. I wondered if the car and truck differed by much.

On some of the other radios that I have worked on, one of the tuning coils usually has no external can so I guess it is not unusual for that assembly to be different.

Just so I understand, your alignment problem was with the oscillator circuit? I had an AD radio a while ago that I hadn't replaced the oscillator cap and the radio was working but it was bringing in signals from the short wave band! I kept tuning in what should have been a local station and got Russian programming!

Fred

Fred,

Yes, the osc circ, the 180pf cap across the coil. Replacing it with a different 180pf made no change. They were running out the end of the tuning range and still not peaking as the Sams states. [before I did any tuning of this radio, it would only receive two stations.]

I had to encrease the value from 180pf to 530pf to get the three tuning slugs to tune within range of the screws. Only problem now is that the local stations are not spread across the dial as they should be, they are bunched up in the middle of the dial.

Does anybody have a boneyard of parts? I would like to find a new tuning assembly.

Don

I got parts, BILL

Bill,

What do you think of this radio? Am I out in left field?

I don't think it has much wrong and I've spent many hours thinking and tweeking. To me it comes down to the inductance of L5 not tracking the tuning of L2 and L4 as the station knob is turned.

There is a slot in the mould of the L5 can where there a ferrite sleeve could be seen if one is inside. If you happen to have radio or tuning assembly to look at (without completely tearring a radio apart) could you verify sleeve/no sleeve?

I love working on old radios, it's been a long, long time sinse I've had one this difficult. It's fun but I must be missing a clue. I'm starting to question my sanity

Don

54,
I had a look at one of my chassis for the auto radio and there is no ferrite sleeve on that coil. Bill seems to have offered you some parts. If he doesn't have what you need, I could part this one out.

Fred

Bill, Fred,

Before I trouble you guys for parts, I'm reassembling this tuning chassis and looking at it more. I've spent a lot of time on it already but I'm just not ready to give up. It's a simple circuit, I must be missing something. I'll let you know.

Don

I've run in to a problem like this before, I should log these things down, I would check out your oscillator circuit., I believe that was my problem , those IF transformers in the 50's GM sets are not my favorite, you can get in to trouble trying align those slugs ,I've seen IF's short between the primary and secondary the only way to find it is voltage check ,high voltage on secondary, I've got around 20 parts sets for that radio, you might want to isolate a suspected problem parts and jump in a know good one , the problem is that the old service info does not take in the fact the radios are now 50+ years old, keep at it I've repaired some fairly bad radios before

Bill,

Thanks for the encouragement, I need it. Surprisingly this radio is very clean, I thought the usual caps and vibrator was all it was going to need. It looked untouched except for tubes so I don't think anyone has messed with it to goof it up. It wasn't pulling in the usual stations so I went for the alignment thinking it would go quickly. I really like the var-cap tuners (I know they take too much space) much more than these slug tuners.

Don

I guess if anything else in that stage was really off it might mess up the oscillator characteristics.

I have always wondered why they moved away from the variable capacitor tuning in the early sets. I guess space and the design of the push buttons may have been factors. I wonder if dirt was a problem in variable capacitors in car radios.

Fred

I've worked on Auto radios with the variable capacitors and the work good, I believe space was the problem with them ,in my collection of auto radios my favorite is a 1930 Transitone ,it's a TRF with 01A's ! at that time there is no real power supply it uses "B" battery's I've also got a 1931 Transitone 3 that uses 24's for RF amp still a TRF, BILL

TRFs are interesting, when did they stop making them? The old batteries were no fun, expensive and didn't last.

A friend of mine that grew up on a farm in south Missouri. Didn't get REA power until he was a senior in high school. His dad limited the family to one hour of radio an evening unless there was something really special happening. My gandpa told the REA that he didn't want those damned poles on his property - they bypassed his place. Family not very happy about that.

I'm not really a radio collector, have a '20s RCA, a nice '38 Zenith and a very nice '30s GE, 55/56 Plymouth radio (not sure what to do with this one).

Don

I thought the TRFs were long gone by the 1930. What are they like to operate?

I have read where the early battery radios were called "farm" radios because a lot of farms were not connected to a public utility. After WWII we in Ontario still had a lot of rural dwellings that were not connected.

TRF's Where popular during the 1920 RCA held the paten on the Superhetrodyns ,so most manufature had to build the TRF, there where tuned in stages , I restore a Atwater Kent model 20 three dialer you tuned each stage and also ran the voltage on the RF tube filaments and with another reostat you controled the Amp tube filaments my Transitone the volume is controled by running up the RF filaments, I also have some early regenitive sets they are a real blast run the one tube is used as a detector and amp it keeps passing the signal trough it, the ocilate while tuning and make other radios around ocilate along with it ,BILL

I'm not working on this radio, waiting for parts.

Here's an interesting wiki:

http://en.wikipedia.org/wiki/Pentagrid_converter

Do you remember the function of all the grids?

Here's the final report on this radio:

Fred had the tuning assembly that I needed. It fit in fine and tuned up just like the Sams manula states. I'm not sure what was wrong with the original oscillator coil, it ohmed correctly.

This radio works great now, just like I remember that they did.

Thanks to all for your help.

Don

That is great news. It is really tough when everything looks and reads correct but it still isn't right.

Fred