[Premium-Rx] Eddystone 1650/9 relay problem.

[GandalfG8 at aol.com]

Hi All

This is a brief tale, well I'll try to keep it brief anyway:-), of a problem 
solved that I felt might be helpful to other Eddystone 1650 owners on the 
list.

I recently bought a 1650/9 in lovely condition. It passed all its BITE tests 
but, other than a couple of strong broadcast signals, was as deaf as a post.
A quick look at the schematic showed that BITE tests are carried out with a 
noise injection oscillator right at the front of the RF stages.
The only sections not in the BITE path are the protection circuits and some 
attenuators etc in the antenna line with a bunch of relays to switch them so 
that seemed like a good place to start.
It didn't take long to establish that two out of five changeover relays of 
one type were effectively open circuit in the normally closed position. The main 
culprit was the relay that switched the RF input between the BITE oscillator 
and the antenna circuit.

The relay in question is a Hamlin type HE321C1200. It's a circuit board 
mounted reed relay with, in my case anyway, a yellow covered central coil marked 
with the part number and the glass enclosed reed mounted inside that.
I assumed at first that the problem was tarnished contacts but it seems like 
it might be more mechanical and possibly due to some distortion even though 
the glass was unbroken. I found that slight pressure on the NC lead would 
restore contact. A bit more pressure than intended and the lead bent.
I thought I might have finished it off completely but it started to work ok 
again!!
We all need a birt of luck sometime:-)

I'm not recommending this as a fix:-) and still want to source enough relays 
to replace all in the set, I've found at least two more on other circuit 
boards, but at least the set is working for now.

Anyone suffering the same problem om a 1650/9 would no doubt find it as easy 
to diagnose as I did but it might not be so obvious in earlier sets without 
the BITE oscillator to provide a clue.

I don't know if these relays were used in other models but thought I would 
share the experience just in case it does prove useful to anyone else.

As far as I can tell this relay is now obsolete....
there's a surprise:-)
I haven't checked fully yet but a search on the Hamlin site earler seemed to 
indicate that one US distributor at least had around 6,000 in stock. That 
seems to good to be true, and might be, but I'll try and contact them later and 
confirm that it is the same relay.
If anyone's interested contact me off list and I'll pass on whatever 
information I get.

regards

Nigel
G8PZR

PS
Once it's up and running it's one heck of a nice radio:-)

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