The internals are absolutely minging, everything is caked in black muck, I wonder if this was due to coal fires. If I remember rightly, Malc mentioned he rented this TV out to a mate until 1984, then it was sealed in cling film before going in the loft. I doubt this is from 45-years in the loft as it was sealed, more like crud sealed in from 1984.
Anyway, I've tested the CRT, initially not looking good, with all three guns down, but I've seen this before and if you leave it cooking with the heaters running just under 8V, it often burns off the cathode crud. We shall see in an hour.
Whilst the CRT is on a slow simmer, I removed the power unit, to reform 7C2, I'll test 7C7 as well. Gave it a good clean while it was out. Big red can is dated Oct 74. I notice a few of the cans over on the Teletext board are dated 77.
Spares
I have a few Z718 boards in stock from a scrapper I bought a few years ago from that chap in Ipswich. I had a look at the power unit I have in stock, it appears a newer release, but one thing I did notice, I thought I'd share here. Have a look at the photo and tell if you spot what I spotted.
Edit:
30 mins in and the CRT is going the wrong way, emissions are decreasing, I'll leave it another 30 mins, but it looks tired. I think this will need a clean and balance.
Despite cooking the cathodes for well over an hour at 8V, which normally burns off the cathode crud, when the heaters were returned to 6.3V and retested, the emissions would not recover and kept falling. However, they eventually stabilised (see below), poor thing is pooped! I've not had such a tired CRT in a long while.
Time to see what a clean & balance may bring.
Chris, Well done with the repair of the remote. The chassis is the Z718. This chassis was designed around the Toshiba RIS? range of crts, 18 inch ( the first sets to appear) 20 inch, 22 inch and 26 inch . There are static convergence adjustments on the neck which can be removed and as far as I can remember the scan coils were bonded to crt and could not be replaced. I recall ordering the complete crt assembly for what I thought was a scan coil fault, unfortunately the fault was elsewhere! Please remember to replace the 910 ohm resister in 12 volt supply. Not sure if the power board was different in only the 18 inch version. Hope this is of help.
Regards,
Oliver.
Hi Chris I would suggest getting a picture on it first before boosting the tube. You may find with a bit of beam current that it comes up and sometimes a tube that reads low will produce a fair picture anyway. Toshiba tubes didn't react well to boosting often going down again after a very short time. Often a boosted one will go down to worse than it was before. If it doesn't look that good with a picture you have the option of increasing the heater voltage a bit to see if it improves this is my preferred method rather than reactivation. Just my thoughts...
Please remember to replace the 910 ohm resister in 12 volt supply.
As mentioned I'm not familiar with this chassis at all, I wasn't aware of this, appreciated the tip, thanks.
Hi Chris I would suggest getting a picture on it first before boosting the tube.
Indeed, I will leave alone, the condition of the internals does seem to suggest high usage.
[...] one thing I did notice, I thought I'd share here. Have a look at the photo and tell if you spot what I spotted.
As no one commented on this, I'm guessing the quality bodge on my spare power unit went unnoticed. Here's a close up.
Ooh, nicely uprated fuse, it’s there to protect the other fuse, by blowing the track off the board instead, saving you the expense of having to replace the fuse!
I actually didn’t see that in the earlier photo, as I was looking on my phone!
Reformed the main can on the Power unit, 7C1 & 7C2 both 300uF @ 325V and checked capacitance, both are OK.
The green is not the usual cap I've seen across the mains, normally I see RIFA or those horrid Dubilier, how do these fair, are they reliable, or do folk change them? Looks like someone in the past caught the edge with their iron.
Hi Chris, not too long ago 9 months or so I did a video on one of this chassis set on YouTube, might be worth you having a look, it's possible to power up the set without the line stage running.
@crustytv Appears to be marked Duopack which to me would mean mixed dielectric, it’s also around the correct size for that type of capacitor.
Mixed dielectric capacitors went S/C across the mains voltage as well as those used as boost capacitor in valve sets.
Hi Chris, not too long ago 9 months or so I did a video on one of this chassis set on YouTube, might be worth you having a look,
Hi Michael, that will be very helpful, I'll see if I can find it on your channel, any idea of the title, did it have Z718 in the title?
it's possible to power up the set without the line stage running.
Again, wonderful, I will definitely want to do that, is it covered in your video?
Mixed dielectric capacitors went S/C across the mains voltage as well as those used as boost capacitor in valve sets.
I think I will replace it with an X2 class.
definatley a must if your not familiar with this chassis as there's a lot of quirks to catch you out, let me find the video title, I won't be able to link it though as I'm not computer literate, and by the way, the difference between the chassis you have and the T20, in your set HT regulation is carried out by the line stage, T20 has its own power supply in the bottom of the set to generate a 200 volt rail.Hi Chris, not too long ago 9 months or so I did a video on one of this chassis set on YouTube, might be worth you having a look,
Hi Michael, that will be very helpful, I'll see if I can find it on your channel, any idea of the title, did it have Z718 in the title?
it's possible to power up the set without the line stage running.
Again, wonderful, I will definitely want to do that, is it covered in your video?
Rank Bush Murphy Z718 chassis vintage colour TV set from 1977.is the video title.
Also I thought I saw another one of these sets or one very similar last night on e Bay in an antique shop.
A Decca set sold the other day for just short of £900, think it was a Bradford.
Rank Bush Murphy Z718 chassis vintage colour TV set from 1977.is the video title.
Wonderful, that's going to be so useful.
I've just removed my line output panel and I need a bath, it's covered in black muck. I think I'm going to move this set outside and try to blow it all out with compressed air.
Anyway, the panel in my set does not have a tripler, there is an EHT rectifier stick the final anode come off that.
I think my set would have originally had the same flyback transformer as yours, these were very un reliable and my set was modified before I got it.
Cleaned the line board, I'd love to know what this black gunk is, it's everywhere, at least now this one bit does not cover me in it.
Checking the parts store, I've found another Z718, line output panel, decoder, if, and power unit, so I do have another lopt and EHT rectifier if the worst happens.
Was it this chassis or the T20 that had a 1 ohm resistor in the base of the line output transistor, it went high approx 10 ohm and blew the output transistor?
It altered the square wave input to a slope that put the transistor in the conduction area that it overheated and shorted.
The transistor being fully off or on giving the lowest heating.
T20Was it this chassis or the T20 that had a 1 ohm resistor in the base of the line output transistor, it went high approx 10 ohm and blew the output transistor?
It altered the square wave input to a slope that put the transistor in the conduction area that it overheated and shorted.
The transistor being fully off or on giving the lowest heating.
Yes, just checked, damn good memories you TV engineers have. 👍
Someone questioned if a mullard tube would be a replacement for a Toshiba black stripe and the answer has got to be yes if blackstripes were in short supply.
Here is an extract from October 1980 rank service skill, describing fitting a A51-570X in the Toshiba designed T24 chassis.
Chris, would this be of any use to you??
