[GreenKeys] Teletype REC11 Rectifier "is NOT suitable for use in the signaling ... circuits of Teletype apparartus"

[Ralph Irish]

After seeing a number of references and replies about the 'oil-filled capacitor', I am surprised that no one made mention of the 
possibility of dangerous 'oil' in these devices? Many, made before the 1960s had PCB based oil in them. There were a few 
'Copyrighted trade names' from come companies. Pyranol, comes to mind, but I can't associate it with any particular company. 

I worked in powerhouses where we had oil filled transformers and up to some date in the 70s, I think, this PCB based oil was 
used as a coolant. We had a replacement program at Ford, where all of the PCB-filled units were removed and replaced with 
transformers using a safer silicon based coolant. There were retro-fill schemes, but they rarely produced low enough levels 
of residual PCB oil. Replacement seemed to be the best way. 

Up to the removal of the PCB units, we had companies come to the plant, take small oil samples from the transformers and do 
chemical testing on the samples to be certain that they had not started to decompose and be less useful as a coolant. I took a 
number of these 'technicians' from substation to substation to get the samples. It was usually a week long process, between 
the sampling and base-line data testing on site. The balance of the samples were taken back to a 'home office' somewhere 
for further testing. 

We had one transformer fail and start to leak the oil on the floor. That caused all kinds of problems. Our boss had to file 
a number of reports with the EPA and we had to rent a large 'semi-trailer' sized generator to replace the transformer prior 
to its removal and replacement. 

That oil is DANGEROUS and I would do what I could to dispose of it safely. Back in the 50s and early 60s, oil-filled caps 
were good. After the hazards became known, no one wanted the responsibility for disposal. Similar to the asbesto- 
related problems today. 

I wouldn't know where to start for safe, legal disposal, but consider replacing the caps with modern ones. You don't want 
loose PCB around your home should a can start to leak. 

Ralph - W8ROI 

----- Original Message -----

From: "Jim Haynes" <jhhaynes at earthlink.net> 
To: "Paul Birkel" <pbirkel at gmail.com> 
Cc: greenkeys at mailman.qth.net 
Sent: Monday, November 20, 2017 9:06:26 AM 
Subject: Re: [GreenKeys] Teletype REC11 Rectifier "is NOT suitable for use in the signaling ... circuits of Teletype apparartus" 

If there is an oil-filled capacitor then the REC-11 probably incorporates 
a constant voltage transformer. You might look on the name plate to see 
if the thing was made by North Electric Co. or Power Equipment Co. of 
Galion, OH. (North acquired PECo). That was Teletype's favorite supplier 
for rectifiers, and they were experts in constant voltage transformers. 

They work on a principle sometimes called ferro-resonance. However that 
term has a completely different meaning in the electric power industry, 
so constant-voltage transformer is a better term. Constant voltage 
transformers are frequency sensitive, so they are rarely used in military 
equipment which might have to be powered from a generator set in the 
field, hence not very good control of frequency. Also you see speed 
governed motors rather than sync motors in military equipment for the 
same reason. 

The Model 19 as used in the field by the military typically had a power 
supply with thyratron tubes to regulate the voltage. And some later ones 
had magnetic amplifier control (saturable reactors) I once had a 
Western Electric power supply for a Model 19 that used a saturable 
reactor, and used a couple of VR tubes as the voltage reference. 


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