Rank A823 - Line/EHT Problem - UK Vintage Radio Repair and Restoration Discussion Forum

Niechcial,Steve · 2nd May 2021, 10:46 pm

I am struggling with this a bit, partly because I only have the circuit for the A802A scan unit and this is fitted with an A802B. The tripler arrangements seem to differ between the two. The A802A has 4 connections on the tripler whereas this (A802B) has 5.
Anyway the fault is that with the tripler in circuit the HT consumption goes up to nearly an amp and blows the 630mA fuse. With the tripler disconnected, the consumption drops back to 350 mA. It is probably the tripler at fault, but I want to be certain of any other possibilities, especially as a tripler is going to be hard to find.

dazzlevision · 3rd May 2021, 1:21 pm

Hello Steve,

What is the model number of your A823B set? I may be able to help with (genuine RBM) service information for it.

Heatercathodeshort · 3rd May 2021, 1:53 pm

Hello Steve, I have a used 823 tripler that I guess must be OK. I would not have kept it if it was U/S. It has three connections plus the EHT output. It has a label on it, Z105.
If you want it I can arrange to get it to you. John.

dazzlevision · 3rd May 2021, 6:45 pm

The A823B chassis was the "BEAB approved" version of the A823A.

According to my records, the factory fitted A823B chassis tripler was made by the USA firm Varo and had the following versions:

Z786, Z969 and 7300 6412 (the latter being an RBM part number, which might refer to one of the "Z" numbers here).

The "Z" items refer to a separate (usually pluggable) sub-assembly (after they ran out of "A" prefixed allocations, I expect).

Niechcial,Steve · 3rd May 2021, 10:54 pm

Many thanks for your help guys. I found a diagram of the tripler's innards on line. There is an internal capacitor connected to the focus output at one end and a lead out wire to chassis on the other end. It had gone almost short ( about 700R). I have some 1nF 20 kv caps, so I just chopped the ground wire from the tripler and inserted the cap externally. It all works well.
Thanks for the kind offer of a replacement John- much appreciated.

2nd May 2021, 10:46 pm	#1
Niechcial,Steve Hexode Join Date: Jan 2007 Location: Beckenham, London, UK. Posts: 373	Rank A823 - Line/EHT Problem I am struggling with this a bit, partly because I only have the circuit for the A802A scan unit and this is fitted with an A802B. The tripler arrangements seem to differ between the two. The A802A has 4 connections on the tripler whereas this (A802B) has 5. Anyway the fault is that with the tripler in circuit the HT consumption goes up to nearly an amp and blows the 630mA fuse. With the tripler disconnected, the consumption drops back to 350 mA. It is probably the tripler at fault, but I want to be certain of any other possibilities, especially as a tripler is going to be hard to find.

3rd May 2021, 1:21 pm	#2
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,608	Re: Rank A823 - Line/EHT Problem Hello Steve, What is the model number of your A823B set? I may be able to help with (genuine RBM) service information for it.

3rd May 2021, 1:53 pm	#3
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Rank A823 - Line/EHT Problem Hello Steve, I have a used 823 tripler that I guess must be OK. I would not have kept it if it was U/S. It has three connections plus the EHT output. It has a label on it, Z105. If you want it I can arrange to get it to you. John. Attached Thumbnails

3rd May 2021, 6:45 pm	#4
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,608	Re: Rank A823 - Line/EHT Problem The A823B chassis was the "BEAB approved" version of the A823A. According to my records, the factory fitted A823B chassis tripler was made by the USA firm Varo and had the following versions: Z786, Z969 and 7300 6412 (the latter being an RBM part number, which might refer to one of the "Z" numbers here). The "Z" items refer to a separate (usually pluggable) sub-assembly (after they ran out of "A" prefixed allocations, I expect).

3rd May 2021, 10:54 pm	#5
Niechcial,Steve Hexode Join Date: Jan 2007 Location: Beckenham, London, UK. Posts: 373	Re: Rank A823 - Line/EHT Problem Many thanks for your help guys. I found a diagram of the tripler's innards on line. There is an internal capacitor connected to the focus output at one end and a lead out wire to chassis on the other end. It had gone almost short ( about 700R). I have some 1nF 20 kv caps, so I just chopped the ground wire from the tripler and inserted the cap externally. It all works well. Thanks for the kind offer of a replacement John- much appreciated.