PYE Australia Circa 1971
SONY DSC
Submitted by member iRob2345
This story was related to me by a person who was in the meeting.
The Service Department were getting many examples of a recently-released 12″ portable returned with complaints of “a hissing noise and a funny smell”.
On investigation, it was found that the top of the selenium “stick” EHT rectifier was arcing over to a metal shield.This was referred to Engineering, who pointed out that an insulating cap was supposed to be in place to stop this from happening. So the other returned examples were checked and none had the cap fitted.
Engineering then checked the BOM (Bill Of Materials) and confirmed the specified cap was included.
Production were called in. “Why aren’t you fitting the cap?”
“We are!” was the reply.
A trip down to the factory floor confirmed the part was being fitted. “I’ve always fitted these” stated the indignant line operator. So with claim and counter-claim flying back and forth, my correspondent decided to research the plastic that was specified in the drawing. It was the same plastic that had been used for years for various brackets and insulators.
A meeting was called, an example insulating cap is placed on the table on a saucer. Reading from a document…. “This cap is moulded from Polypropylene. Polypropylene is highly inflammable”
(Produces a lighter and ignites the cap) “It burns with a blue flame and leaves little residue save for a small amount of ash, which is primarily a salt…” (Another meeting participant wipes his finger on the saucer and tastes it) “….which is toxic and highly carcinogenic”!So the mystery was solved but it left a bad taste in the mouth!
Surprising what high voltages and heat can do to materials. Presume the plastic type was changed to a more stable type for that job.
Ekco had a problem in the late 50’s early 60’s with the plastic they used for the LOPTX, it disintegrated especially around the EHT rectifier valve anode connection. I don’t know what type of plastic it was but the problem would affect all their sets after about 5 years. I understand a new plastic housing was available and the windings could be transferred over. I never tried that, a replacement LOPTX would take around 10-15 mins in the house so that’s what I did. Going out to one of those sets I always put a LOPTX on the van in case it needed replacing. Perhaps they changed the plastic in replacements, didn’t do the job twice, or perhaps the sets were scraped after 10 years use.