Regentone 17 -18 thermistor - UK Vintage Radio Repair and Restoration Discussion Forum

regentone001 · 5th Jun 2016, 9:35 am

Hi guys
just tidying up this chassis after finding the frame collapse fault and fixing it and I noticed half of the thermistor between the scan coils and opt is missing, it's R91 on the manufacturer's circuit and is a Plessy CE53905. How will this affect the set? Can I just take it out of circuit? Is a replacement available?
Thanks
Steve

ukcol · 5th Jun 2016, 10:07 am

If memory serves these thermistors were to compensate for changes in scan coil resistance with temperature. If it was not in circuit I would expect a bit of picture height drift as the set warmed up.

Restoration73 · 5th Jun 2016, 3:58 pm

A low value ntc type eg VA1086, VA1033 was often used, a modern type may be
http://uk.farnell.com/epcos/b57153s0...-3a/dp/1688794

regentone001 · 5th Jun 2016, 5:07 pm

Hi guys thanks for that. I have ordered a new thermistor and will let you know how it goes
Steve

regentone001 · 11th Jun 2016, 7:06 am

Hi guys. Well the new thermistor arrived and I have finally got around to fitting it. Whilst I had the set apart I also tidied up the components I had tacked in when tracing the frame collapse, so a new R64 820k, C57 0.05uf, R41 33k, were fitted. I also fitted a new R27 27k and R31 10k which had gone high. I also found that I had fitted the replacement for MR5 in the AGC circuit the wrong way around, which explained the lack of difference the Contrast control made. Now the set is far more stable, touch wood, I used it for 3 hours last night and no frame jitter. There is a lot more contrast, it was OK before but now its great. The frame is really linear and stays that way.
(All component numbers used are from the manufacturers manual)
Thanks for all the advice and help.
Steve

5th Jun 2016, 9:35 am	#1
regentone001 Heptode Join Date: Sep 2014 Location: Coventry, West Midlands, UK. Posts: 519	Regentone 17 -18 thermistor Hi guys just tidying up this chassis after finding the frame collapse fault and fixing it and I noticed half of the thermistor between the scan coils and opt is missing, it's R91 on the manufacturer's circuit and is a Plessy CE53905. How will this affect the set? Can I just take it out of circuit? Is a replacement available? Thanks Steve

5th Jun 2016, 10:07 am	#2
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: Regentone 17 -18 thermistor If memory serves these thermistors were to compensate for changes in scan coil resistance with temperature. If it was not in circuit I would expect a bit of picture height drift as the set warmed up.

5th Jun 2016, 3:58 pm	#3
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Regentone 17 -18 thermistor A low value ntc type eg VA1086, VA1033 was often used, a modern type may be http://uk.farnell.com/epcos/b57153s0...-3a/dp/1688794

5th Jun 2016, 5:07 pm	#4
regentone001 Heptode Join Date: Sep 2014 Location: Coventry, West Midlands, UK. Posts: 519	Re: Regentone 17 -18 thermistor Hi guys thanks for that. I have ordered a new thermistor and will let you know how it goes Steve

11th Jun 2016, 7:06 am	#5
regentone001 Heptode Join Date: Sep 2014 Location: Coventry, West Midlands, UK. Posts: 519	Re: Regentone 17 -18 thermistor Hi guys. Well the new thermistor arrived and I have finally got around to fitting it. Whilst I had the set apart I also tidied up the components I had tacked in when tracing the frame collapse, so a new R64 820k, C57 0.05uf, R41 33k, were fitted. I also fitted a new R27 27k and R31 10k which had gone high. I also found that I had fitted the replacement for MR5 in the AGC circuit the wrong way around, which explained the lack of difference the Contrast control made. Now the set is far more stable, touch wood, I used it for 3 hours last night and no frame jitter. There is a lot more contrast, it was OK before but now its great. The frame is really linear and stays that way. (All component numbers used are from the manufacturers manual) Thanks for all the advice and help. Steve