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Old 01-25-2018, 01:46 PM   #16
Yuri D.
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Also look for cold solder joints. Several radios have come back to strong life after refreshing the solder joints around the stages, etc.,
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Follow-up
Old 02-27-2018, 09:21 AM   #17
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After reading all the applicable posts, I discovered that my primary problem was probably the EUa-4.
There was an unacceptable voltage drop when all tubes were installed in the UKWE.e. I got the 5KOhm 5Watt and 8Ohm 20Watt resistors suggested on another post, creating the appropriate load for the Umformer to duplicate the receiver load. Output dropped from 130V to about 109V, which isn't going to work.
I decided to disassemble, clean and inspect this Umformer. Bearings seemed OK. Lubricated with what appears to be white lithium grease. Sealed (more or less) bearings. Oddly, they say "Made in Sweden" in English and French on the outer race, so I assume they were replaced. For reasons I won't get into, I decided to replace these bearings. Should anyone need to do this, they are 22mm OD, 7mm ID and 7mm deep.
So I will reassemble all this, look at the capacitors and see if there is improvement.
Excuse my ignorance, but what component is the "collector" to be cleaned?

I seem to encounter more than my share of altered equipment. While my project UKWE.e is complete and original looking, I noted that several of the trimmer capacitors seem to have been changed out for fixed capacitors. They are approx. correct value, and a very old style like some originals I have seen. So when the Umformer is up and running, other challenges remain.

BTaylor
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Old 02-27-2018, 11:10 AM   #18
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Actually, most of the bearings say "Made in Sweden" in these Umformers - so original. Sweden was one of the major sources of ball-bearings for Nazi Germany.
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Old 02-27-2018, 12:33 PM   #19
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Quote:
Originally Posted by BTaylor View Post
After reading all the applicable posts, I discovered that my primary problem was probably the EUa-4.
There was an unacceptable voltage drop when all tubes were installed in the UKWE.e. I got the 5KOhm 5Watt and 8Ohm 20Watt resistors suggested on another post, creating the appropriate load for the Umformer to duplicate the receiver load. Output dropped from 130V to about 109V, which isn't going to work.
I decided to disassemble, clean and inspect this Umformer. Bearings seemed OK. Lubricated with what appears to be white lithium grease. Sealed (more or less) bearings. Oddly, they say "Made in Sweden" in English and French on the outer race, so I assume they were replaced. For reasons I won't get into, I decided to replace these bearings. Should anyone need to do this, they are 22mm OD, 7mm ID and 7mm deep.
So I will reassemble all this, look at the capacitors and see if there is improvement.
Excuse my ignorance, but what component is the "collector" to be cleaned?

I seem to encounter more than my share of altered equipment. While my project UKWE.e is complete and original looking, I noted that several of the trimmer capacitors seem to have been changed out for fixed capacitors. They are approx. correct value, and a very old style like some originals I have seen. So when the Umformer is up and running, other challenges remain.

BTaylor
The collector are the segmented brass bits on the rotor that are in contact with the brushes. All the current has to flow via the brushes into the rotor and out again via the collector. If the collector surface is dirty it creates resistance, causing a loss of power and a voltage drop, just the sort of thing you were suffering from.

You clean it by using emery paper and a bit of contact spray. You need a wooden or plasic bit about 1 cm wide to which to can fix a strip of emery paper (Fold it double around the wooden bit and fix it at the top with a small elastic band or something similar). In any case use an insulating material to hold the emery paper so you won't electrocute yourself... With the Umformer running, you gently hold the emery paper against the collector until it turns brass colour. Clean any residue off with a cotton bud or two. When you use contact spray, there may be some sparking and slowing down of the umformer, but when clean and dry it should run without sparking. If sparking persists you need to replace the brush capacitors.

The umformer now just needs to run for a while to form a new patina on the collector (it should turn a nice shiny blueish colour).

You may want to check if the brushes are not to far gone, the top of the brushes should be about level with the top of the brush holders. They can sit a few milimeters deeper, but the brush springs should have plenty of push.

regards,

Funksammler
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EU4a follow up
Old 03-25-2018, 04:55 PM   #20
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I have two Umformer units. Neither showed much wear on the collector, but both were putting out about 110V under load.
I wanted to grease/inspect the bearings, so I cleaned and thoroughly polished the collector while it was apart. I replaced one bearing on each Umformer. I did this as a precaution, because, without detailed disassembly instructions, I was concerned that I could have damaged the races. These bearings are DIFFICULT to remove. I cut them off with a Dremel cut-off wheel, cautiously cracking the inner race to get it off the shaft.
After reassembling them, and running in the brushes, with a couple of follow-up applications of contact cleaner, they both put out steady 130V under load. Success!
B Taylor
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Old 03-26-2018, 02:40 PM   #21
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Congratulations! Does it solve your Ukw.E.e problem?

regards,

Funksammler
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Old 03-27-2018, 12:13 PM   #22
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Quote:
Originally Posted by BTaylor View Post
I have two Umformer units. Neither showed much wear on the collector, but both were putting out about 110V under load.
I wanted to grease/inspect the bearings, so I cleaned and thoroughly polished the collector while it was apart. I replaced one bearing on each Umformer. I did this as a precaution, because, without detailed disassembly instructions, I was concerned that I could have damaged the races. These bearings are DIFFICULT to remove. I cut them off with a Dremel cut-off wheel, cautiously cracking the inner race to get it off the shaft.
After reassembling them, and running in the brushes, with a couple of follow-up applications of contact cleaner, they both put out steady 130V under load. Success!
B Taylor
I wanted to learn how to repair rotary transformers by the most practical way: repairing a very damaged one. I had some problem and the project failed...but I learnt how to change bearings: With a bearing remover!!!

see the link, it might help:

http://www.wehrmacht-awards.com/foru...d.php?t=564656


Carles
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looking for a Kar 98k bolt in working condition numbered 2020, please let me know if you have one.
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Gear Puller plus
Old 03-27-2018, 08:44 PM   #23
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Default Gear Puller plus

Carles -

I had read through your account (sad outcome!) before I worked on mine. I have a mini gear puller like that, but it wasn't compatible with my shaft. Anyway, the bearings were incredibly tight. Some polishing was even needed to install the new bearing without damaging it.

Funksammler -

I have one Ukw.E.e that now works well. Not the one I was posting about. There is a commercial station I can normally pick up on the low end of the frequency range. It came in strong but sort of garbled and poor. Cautious adjustment of the center screws of the block shaped coils - 5 of them - made a dramatic difference. Now the sound quality is quite good. And this is on the "Nah" setting, and no antenna. It looks like the "Nah" setting doesn't utilize the antenna, anyway. Connected to a proper antenna and using the "Fern" setting remains to be tried.
So I still have troubleshooting to do on another Ukw.E.e. I checked the resistance range on the volume potentiometer and it is real close to the other functional radio, so I need to look elsewhere. Tubes are not involved. I occasionally can get a loud scratchy sound out of it, but nothing predictable and it doesn't vary with tuning. I will continue to trace the circuits and see if anything looks suspicious. Testing all capacitors would be a nightmare. It is a "yellow stripe" radio that had some tinkering done with it, but not that much.

BTaylor
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Potentiometer Follow-up
Old 04-02-2018, 08:30 PM   #24
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Default Potentiometer Follow-up

To any who have followed this:
Found a simple but maddening issue with the volume control potentiometer. It had a very weak and intermittent ground. It grounded through the chassis rather than having a dedicated ground wire. Not surprising. The nut that secures the switch/potentiometer to the chassis was slightly loose, so that the entire switch moved slightly when the knob was turned. Tightening the nut worked wonders. Now I have consistent, but not very good, reception. On to the next stage, I guess!

At least I reconditioned my Umformers and found a few "issues" when studying the wiring diagrams. Still learning.
BTaylor
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Faceplate repaint
Old 04-18-2018, 06:41 AM   #25
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Default Faceplate repaint

Here is the finished faceplate of the Ukw.E.e shown earlier. Getting paint of an acceptable color and gloss level was not easy. Color may be slightly light,,,
The plastic in the frequency window is replaced. As far as I can tell, this is very close to the appearance from the SABA factory, 1942. Could have been repainted gray during the war. If paint had been original, just worn and weathered, it might have been better to leave it alone.
B Taylor
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Old 04-18-2018, 03:04 PM   #26
Yuri D.
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Looks awesome!
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