HMV 1644 Radiogram

[signalman4]

Hi folks,

I've been reassembling and repairing this lovely radiogram and there is a metal box covering the area where the two EL84 valves are located.

Can anyone tell me why this box is there because in my view it impedes the airflow around the valves and they do get quite hot.

These are a new matched pair and the bias is correct so no worries there but I feel inclined to take this box off to allow better airflow.

Thoughts welcome.
Cheers.

[Terry]

X-Ray screening?

I must admit that, despite the cooling slot in the (very low!) roof, I find this idea bizarre!

If someone can come up with a viable explanation for its existence, I will be very interested to read it!

[Crackle]

What is above the 2 valves, is the metal screen there to help deflect heat from something that is more sensitive to getting too hot.

Mike

[pwdrive]

Anything to do with the reverb?

Lawrence.

[signalman4]

Hi guys, thank you for your replies.

There is loads of space above the box - must be 10 or 12 inches of virtually open space. At the rear of the chassis are the mains and output transformers and in front of those is one PCB that carries all the audio circuits. The IF and reverb amplifier circuit boards are fixed to the back of the tuning dial frame.

The Hammond reverb unit is in a compartment of it own behind the right hand record storage cupboard. There is an aperture in the back panel so it can be seen in all its glory! I have done some work on the reverb unit when I found I had no resistance measurements on either the input or output phono sockets. After a lot probing around, I found the connections from the coils to the phono sockets were all o/c. The connections were made using a very lightweight tinsel flex. Over the years of not working, the dampness was absorbed into the fabric covering and the copper tinsel corroded and the coils became disconnected.
At the moment, I haven't been able to check the reverb unit properly as one of the phono plugs is broken and it doesn't make contact.
They are rusty old things from the 1960s so I thought I would put a couple of new ones in there.

Its a mystery why this box is there over the EL84s. I tried to see if any other near models (1643 & 1645) have it but as far as I can tell they don't.

[Radio Fixer]

"ealth and safety".  Cant take a chance on service people or an inquisitive child getting burnt can we   

Gary