My Pye B18T has been the flavour of the month in the front room, all has been well until last night when we switched on and were met with a raster with a floating pattern. The set has been recapped and all the resistors out of spec were changed a year or so ago, the valve pins on all the EF50`s are clean.
By chance I found unplugging, then plugging back in V2 (EB41) the fault was cured until the next turn on. Initially I suspected a bad socket but this has been discounted when I fitted a new one.
One half (a) is the vision detector, the (b) side is the interference limiter.
What would be a good choice of diode to use as a temporary measure in place of this valve ? my thought would be a 1N4148 ?
A new EB41 has restored normal operation, the old one tests fine 
Hi Stephen,
I wonder if the valve socket is slightly dodgy ?
Perhaps the replacement valve is a better fit / connection ?
Marc.
Marc
BVWS member
RSGB call sign 2E0VTN
I prefer connecting a battery to the heater and measuring the diodes and the H/K with a diode tester.
You might find something that does not show up on a valve tester.
I might give that test a try, the valve socket is a new one. The original valve works fine in the the other two sockets.
Does anyone know the purpose of the rubber grommet type arrangement that holds the EF50 valve sockets down ? They are decidedly ropey on this chassis with a couple that have let go, allowing the socket complete with rivet pin to drop slightly.
I am unable at this stage to see a solution to remedy this even with a new socket as the chassis has been punched out at 5mm for the rivet / grommet.
Ideas please if this has been encountered before, which it must have.
Does anyone know the purpose of the rubber grommet type arrangement that holds the EF50 valve sockets down ?
Sounds like an anti-microphony arrangement to me...
So I would be best trying to find a similar grommet to go back 
. I had a feeling this might be coming
So I would be best trying to find a similar grommet to go back
'fraid so...
I have encountered two types of vibration isolators on audio amplifiers that share their chassis with machinery that creates vibration.
On the left is an output pentode holder with a special rubber part enclosed in a special bracket clamped to the chassis. This kept them cool and they are in remarkable condition for their age.
In the centre are some that are simple grommets that are still manufactured and can be bought in boxes of 100 for a couple of quid. These suffered heat damage and there was no problem getting replacement parts.
Not the best picture but it illustrates the issue.
Those look like the natural rubber cable entry grommets that I replaced on the sub chassis in my set.
The valve holder will have sagged as did the sub chassis in my case and the solution will be the same.
I have almost certainly got some left in stock if you are desperate or I could post the part number and size if you need loads of them.
The new ones will be black as mine were.
This is the dimensions of the grommets used; maximum of eight I think would be needed.
The ones I have in stock are 5mm and I stretched them over the screws.
There was a misprint in the website when I bought them.
The correct size is on my next shopping list and due to a shortage of money this will be delayed.
I also have 14mm.
Who is this supplier, they seem quite useful?
Closest I can find so far has a minimum Qty of 500 or £30 minimum order 
I got mine from Farnell.
There may be some value in backing off to cable accessories.
4mm hole size 46p/10
6.3mm hole size 65p/10
PVC rather than rubber ...
http://www.partridgeelectronics.co.uk/01Bcablesetc.htm
Fourth item from the bottom of the page.
When all else fails, read the instructions
Just got off the phone from supplier who has almost perfect size, just 1mm larger external diameter. Also they are oil resistant and white, he is checking that they are able to supply <500 QTY
500 = £8.50 but I would never use them.
Thanks for looking Terry, I saw the grommet listing on Partridge but didn't see those sizes though.
Grommets Ltd. are very useful suppliers, but you may find the MOQ is an issue for small orders - I just make the order up a bit to cover it, and they are in proper rubber.
I've often wondered how much a custom moulding of a 9" CRT mask would be...
