Vintage Synth Repair

My background on transformers is that I used to design them and I can assure
you that at no time did I ever have the need to put a thermal fuse inside of
them.  Fender use thermal fused transformers a lot but it is not the norm.
The main reason why they use them is to reduce the cost by taking them down
to the minimum size they can get away with but this has the unfortunate
result of raising the temperature they operate at!  Properly designed a
transformer has no need for a thermal fuse.

 

I know of no law that requires thermal fuses, but I'm open to those with
better knowledge than me.

 

Regards

Brian G3OYU

 

From: vintagesynthrepair@yahoogroups.com
[mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of HAL9000
Sent: 01 June 2011 5:29
To: vintagesynthrepair@yahoogroups.com
Subject: Re: [vintagesynthrepair] Re: Crumart Trilogy replacement power
transformer

 

  

 

Sorry I disagree, I have met with many with thermal fuses if not to say most
of them. One I'm thinking of at the moment was of a high end Technics
Arranger (now operating no more) that was still new at the showroom brought
to me dead. In some tropical countries they do go o/c because of
insufficient ventilation not like other much colder countries.

I'm not into transformers as I give them to my winder for repair but could
be thermal fuses in them are for safety reasons stipulated by law.

 

H9000

 

  

This is misleading very few transformers have built in thermal fuses!

Regards

Brian G3OYU

From: vintagesynthrepair@yahoogroups.com
[mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of HAL9000
Sent: 01 June 2011 8:21
To: vintagesynthrepair@yahoogroups.com
Subject: Re: [vintages ynthrepair] Re: Crumart Trilogy replacement power
transformer

  

I check the transformer's primary using a self-made (lopt) inductance tester
running at 19KHz. The primary could have shorted turns due to overheating
etc., althought usually there is a thermal fuse incorporated inside the
transformer as protection that goes o/c. If it blows the main fuse (verify
if this is correct) with the secondary disconnected then it is surely bad.

H9000

  

The psu board could be faulty but I haven't even got that far. Right now
just having the transformer connected to the and power switch (with the rest
of the synth disconnected) still blows the fuse. The primary checked out.
The secondary show something like 3.5 megaohms. That was it. There may very
well be more damage further on but as I said, I haven't got that far yet.