BRC 960 Heat Shield

[Focus Diode]

As previously mentioned in an earlier thread the sound output stage is mounted directly above the line output stage valves in this model. They should be a heat shield which would absorb much of the potentially damaging heat which a previous "engineer" had failed to replace following service work many years ago.

Dazzlevision, who brought this to my attention, kindly uploaded some photos of the heat shield in his Ferguson model. His photos are towards the bottom of this page:

https://www.vintage-radio.net/forum/...=103917&page=2

I had made a temporary replacement which had some effect, but recently the inevitable happened when the sound took longer than usual to appear, then falling to a low level with distortion in use.

Having changed some high in value resistors a new PCL86 was also required. The resultant sound is now better than ever with plenty of volume. Now to think of a more permanant replacement heat shield.

A look in the junk box revealed two pieces of aluminium which, as luck would have it, fitted comfortably above the PL504 leaving a useful gap between the valve and PCL86 underside components without risk of shorting the latter out despite the limited space. In common with the original heatshield a further slab of aluminium was bolted on to further absorb the heat.

I don't pretend for a moment the replacement shield is cosmetically good, nor does it equal the effectiveness of the original long missing one. The results look promising after a temperature check after some use, having switched the set off first of course.

Cheers,
Brian

[Restoration73]

The PCL86 glass may get hot, so may be worth routing the speaker leads further away.

[Nuvistor]

hi Brian,
How reliable were these sets, there is a lot of heat in a small cabinet?
Frank

[FERNSEH]

Back in the sixties I often came across TVs with missing metal screening boxes and plates. The most common omission was the screen around the line output stage in Ekco TVs
Also, like Brian's BRC 960 set metal heat deflectors were missing after some telly man had "serviced" the set.
It was always good policy to refit these parts and the return the set back to it's original specification.

DFWB.

[HamishBoxer]

LOPTX screens and tuner cans always missing in my servicing early days too.Bit like the backs off tv and radios now.

[Focus Diode]

Originally Posted by Restoration73

The PCL86 glass may get hot, so may be worth routing the speaker leads further away.

Absolutely right. The leads don't touch the valve envelope as it may appear in the photo, nevertheless I will be reposistioning it once I dismantle the set to clean the CRT face and implosion sheet again when time allows. This time I'll be adding a dust seal, something I should've done last time.

As previously mentioned these sets are basically a 950 chassis "wrapped up" to fit a small cabinet, sets with this chassis range from 11" to 27" CRT sizes. As one can imagine these 16" portables do get very hot in operation! As for reliability when they first came out I don't know. This HMV version certainly has reliability issues.

In retrospect I should've carried out further preventitive maintenance earlier, such as replacement of the original dropper capacitor before it had the chance to fail. Should another example turn up I consider it essential to replace this component on sight.

Re the heat shield it's most unlikely a genuine one will turn up.

Many thanks to you all for the feedback.
Cheers,
Brian