One of my recent purchases is a Ferguson 3643 'Courier'.
A work colleague was kind enough to collect this set and it was delivered to me today, so here's a first look over it.
Front view.
Seems to of been looked after and stored quite well. Some paint has started to flake off from the lower section of the tube surround.
Rear view.
Clean back panel with telescopic VHF and loop UHF aerials. The bowler has a few marks on it like something quite hot has touched it.
Chassis view.
Chassis looks to be in really good condition with just a thin layer of dust. Nothing seems to of been stressed or got hot.
Dropper.
Line output.
UHF/VHF tuner.
Mains plug.
I don't think this has been plugged in for many years.
One question I have is this. Is this a late version of the 950 chassis for 16" sets as quoted in the Trader sheet and the red books or a 960 as quoted in the BRC chassis guide on here?
https://www.radios-tv.co.uk/brc-thorn-chassis-guide/
https://www.radios-tv.co.uk/brcthorn-chassis-bulletin/
Jon
Jon
BVWS Member
That does look good ! A little used set and will make a great project. Well done for acquiring it Jon.
The bowler has probably been in contact with another plastic/PVC item and has reacted.
To understand the black art of electronics is to understand witchcraft. Andrew.
Looks really nice, definitely a 960 but the version with a conventional heater chain rather than the one using a 4.3uF capacitor as a Wattless dropper. Fellow member Focus diode has an HMV 2633 with the latter arrangement, see here.
https://www.radios-tv.co.uk/community/black-white-tvs/frame-transformer-for-brc-960/#post-679
John.
John.
Hi,
I am working from trader sheet 1895 which says it is for this model and the chassis layout is identical (2 section dropper/conventional heater configuration).
Because of the clean and what looks like untouched chassis I decided to apply some volts via the variac. I started at about 50 volts and left it for about 30 minutes, a quick check around with the Fluke suggested all was well. Next up to 100 volts still all OK. While I was doing this I got the pattern generator ready and connected up just in case it all fired up. At about 180 volts I could hear crackling from the speaker when the volume was adjusted. I gave the UHF tuner a spin and was pleased to hear the test tone, even if it was quiet and distorted. A few more volts and the sound improved and I think I can also hear the frame stage running. A few wisps of smoke started to rise from what I thought was the dropper, but wasn't sure so I switched off and had a check for signs of distress, none could be found. I switched back on again to the same mains voltage as before.....no smoke and test tone is still present.......then it disappears then it's back and is now in a regular cycle. A few more volts and this time more smoke and I can see it is coming from under the flywheel sync PCB. Switched off again sharpish to investigate. After removing the flywheel sync PCB I can see that R27 and R28 don't look very well. I have just taken both items out for checking, R27 (cathode bias 100R) is measuring 50R and R28 (HT feed 5K 1W) is measuring 380R. These parts are associated with V4 a 30FL14 vision IF, the other section of this valve makes up the line OSC. After replacing both parts I tried again. As soon as the HT reaches about 160 volts the cycling begins and the volts on the anode drop to about 4 volts (smoke starts rising) then returns to 160 volts and the cycle continues like this.
Jon
Jon
Jon
BVWS Member
R27 and R28
Jon
Jon
BVWS Member
Odd.... thinking intermittent heater-cathode short somewhere possibly?
To understand the black art of electronics is to understand witchcraft. Andrew.
Hi Andrew,
As I cant hear line whistle, I'm wondering if V4 is breaking down/faulty and the fault shows up when the line osc tries to start up???
Jon
Jon
BVWS Member
Hi Jon, it's possible....were those resistors burnt out before you applied power?
To be honest, I'm not familiar with this set but in any case, I would recommend some cold checks for any shorts before applying power.
To understand the black art of electronics is to understand witchcraft. Andrew.
Hi Jon, it's possible....were those resistors burnt out before you applied power?
I don't really know Andrew, as they live under the flywheel sync PCB they are hidden from view. The PCB on the component is darkened under the HT feed R28, but that could just be from normal use. I also found it odd that both resistors had gone down in value.
Jon
Jon
BVWS Member
Hi Jon, it's possible....were those resistors burnt out before you applied power?
I don't really know Andrew, as they live under the flywheel sync PCB they are hidden from view. The PCB on the component is darkened under the HT feed R28, but that could just be from normal use. I also found it odd that both resistors had gone down in value.
Jon
Oh yes, they certainly can go down as well as up, especially when over-loaded..... anything can happen. Once I can find the data, I'll have a gander ?
To understand the black art of electronics is to understand witchcraft. Andrew.
How burned is the PCB, it’s possible the PCB material around the valve base is breaking down?
Presume you don’t have a 30FL14 handy?
Frank
Hi Frank,
I don't think the burn is that bad and seems to be confined to where the resistor is mounted as is sits vertically. I don't have any 30FL14's but I do have some PCF808's, but I can't get at them at the moment. Here is the area of the PCB. I just tacked in a 4K7 1W for testing purposes.
Jon
Jon
BVWS Member
[..] Once I can find the data, I'll have a gander ?
You need to look in the data library under Television | TV P-T
Trader sheet 1895 will be the first file you see.
There are various other 950/960 service data papers to be found around page 6/7 of that library section as well.
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Has you say the PCB doesn’t look too bad.
The cathode resistor could be an old fault and the burn up of the 5K may well just be down the the ceramic decoupling cap.
Frank
Has you say the PCB doesn’t look too bad.
The cathode resistor could be an old fault and the burn up of the 5K may well just be down the the ceramic decoupling cap.
I will have to do some more investigation. Its the cyclic nature of the fault that puzzles me and the apparent lack of line stage operation derived from the same valve, maybe just a coincidence and I actually have two faults? The same fault also exists on 405 line. I will need to get into the loft to find my spare PCF808 and try a substitute.
Jon
Jon
BVWS Member
Valve replacement is usually the easiest first choice, not quite so easy having to climb into a cold loft and hunt around with the thought, where did I put the things. ?
Frank
I do know which box they are in and I also know where that box is, it's the mountain of other junk useful stuff that is stacked up in front of it that I will have to move to get to said box!
Jon
Jon
BVWS Member
An internal electrode short in V4 pentode that is probably occurring as the valve heats is the only possibility I can see, then as it cools due to the short, it opens again only for the cycle to repeat.
Looking at the circuit, I can see nothing to cause that amount of current flow other than a short.
To understand the black art of electronics is to understand witchcraft. Andrew.
As I can't face going into my loft store and having to move quite a lot of stuff, I have just purchased 2 NOS Mazda PCF808's from eBay. So I will wait for those to arrive before continuing with this set.
Jon
Jon
BVWS Member
So you will probably have another valve to take up into the loft, will you put it with the other PCF808’s? ?
Frank
