Introduction
Before I moved over to colour I started on Black & White Television, I collected in excess of 50 sets before finally moving them along to finance my colour TV collection. I have however kept a couple of sets that are special to me, here is one of them.
Dual Standard
Model: Bush TV125CU
The “U” denotes that the UHF tuner is installed
Year: Released August 1963
Cost: Originally cost £83 11s 5d plus purchase tax
System:405 Line 625 line
Valves: V1 PCC89,V2 PCF86,V21 EF85,V22 EF80,V23 EF80,V24 PCF80,V25 EF80,V26 PCF80,V31 PCF80,V32 PCL85,V33 PCF80,V34 PL36,V35 DY86,V36 PY88,V25 EF80,V26B PCF80,V38 PCL82,V41 PC88,V42 PC86,
CRT: CRT AW47-91
General Information:
Filter cap C346 snipped and mains applied, low and behold the screen lights up.
Some cap changes around the line stage
I carried out the recommend TH32 modification as this set had the original configuration. This involved swapping the positions of TH32 (Thermistor ) with R358 , then changing R358 to a 10R-10W. This saves the thermistor as it now only carries heater current. Also cleaned the system switch contacts
The VHF push button tuner was operating very poorly, the buttons felt sluggish and did not lock correctly. The tuner was removed, gunk removed cleaned and oiled. Smooth operation returned.
Vision buzz from speaker overloaded test card with little or no control over contrast, this all turned out to be VR21 (agc delay) and VR22 (Vision limiter) both being set incorrectly.
Over-wind trouble, HT started at 218V then dropped to around 187V accompanied by loss of width (see below) to the raster. The set was left running, the moisture in the winding seemed to boil off as the HT rose back to 218V along with full width raster. The set was soak tested for 8 hours without issue.
Final two shots show the restored set and the two resulting test cards on 405 & 625 lines
405 Line operation
625 Line operation
A great picture with excellent convergence and perfect grey-scale.
(As I’m sure L.Lawry-Johns would have said!)
Another worthwhile and interesting restore.
This site just gets better and better !!
I liked this chassis, easy to repair and on the whole reliable. They had a few stock faults but I did not have many difficult to repair ones.
I would love to try a TVs restoration was this an easy one to start with.
Regards
Robin
The TV-125 chassis was legendary with TV DXer’s. Not only because of its gain especially when fitted with the later transistorised UHF tuner, but because you could separate the cable to the timebase side system switch, mod the video switching to leave it in UHF reversed video modulation and run the IF and tuner in VHF mode to receive VHF foreign signals from Eastern and Western Europe and Scandinavia.
When these sets first appeared, they weren’t fitted with a UHF tuner. These were much easier to ‘convert’ to 625-line VHF if one was in the workshop during a ‘lift’.
We just stuck two small insulated screwdrivers between pairs of the (vertical) system switch contacts which just hung there and connected HT to the VHF tuner and the IF output to IF input!
The beauty of it, using customer’s property in a busy workshop, was that it was instantly reversible to normal operation when required!
I had one of these unconverted sets running on soak test one Wednesday afternoon (half day closing) in 1966 doing a bit of overtime and, as the conditions were right, I did the two screwdriver conversion and found Rai Uno – the first (and only) time I ever saw pictures from Italy.
Apart from old Fred, the electrician, downstairs, there was nobody else in the building. Fred came up to ask me something, so I showed him the test card and explained where it came from. Then it faded out and, a couple of seconds later was replaced by a gorgeous continuity announcer quite unlike any anybody on UK television. There was no sound, of course but after short time she was replaced by the Eurovision card that used to precede such programmes in those days with the originating broadcaster’s initials in the middle. However, in this case it read BBC/ITA! The proigramme started and the opening credits proclaimed WORD CUP ’66.
So we were watching a programme which been sent over a thousand miles from London to Italy and then over a thousand miles back again to us! And it had only started its trip about 25 miles away.
So, does this count as long distance television or not?
I have the same one! It’s a beautiful set. Any idea how long it should take to warm up? I’ve been leaving it on for small amounts of time as it hasn’t been used in many years but I don’t think I have been giving the valves enough time to warm up.
Hi Cameron,
Thank you for your comment.
With regards to your query, you state very little about the circumstances of the TV in your possession so a lot of assumptions have to be made. The assumption is that it has been serviced by a qualified engineer or competent amateur and as such is in working order. Hopefully not just recently bought after having sat dormant for the past 40-50 years with expectation that it will just work.
Therefore assuming it has been repaired to working order, when the TV is powered on and the valves observed from the back of the set with the cover removed, you should immediately (a matter of seconds) see all the valve heaters glow, including the CRT at the very neck end. You should over the next 10-20 seconds start to see some of the valves at the rear gain in intensity (glow-wise) as they heat up draw full current. Within 30-40 seconds you should have sound and a full raster on screen.
As this is a dual standard 405/625 line TV, depending on which standard is selected and how good your hearing is you should be able to hear the 10,125kHz line stage running on 405-line, a very distinctive very loud whistle. If on 625-line and depending on your age you might be able to hear the 15,625kHz line stage whistle. To view content on 405-line you will have thought about purchasing and standards converter such as the Aurora or HedgHog. To view content on the 625 line standard you will have purchased a UK modulator.
If you just bought this and powered it up hoping as I suggested in the opening paragraph, it was going to work, then you are in all probability going to be very disappointed.
The set in this circumstance will need work to get all the various stages of the TV working. You will need an understanding of vintage electronics, Television circuits and safety precautions. You will need to have access to service data, understand how to interpret that data and have a multimeter, soldering Iron parts such as capacitors, resistors and diodes and possible an oscilloscope should you have tricky faults to diagnose.
Even after all that your biggest problem with the TV125 series will be the LOPT (Line Output Transformer). This was and still is the Achilles heel of the set. It will likely have the usual problem where after a few hours use the HT will start to drop, accompanied by the picture starting to shrink. The LOPT will start to bubble and cook and will eventually fail.
This is due moisture ingress and also a breakdown of insulation between the internal LOPT windings, there are however a few solutions. One is to have the LOPT professionally rewound which is worth it but comes at a cost. The second is to dismantle the LOPT and repair the insulation between the windings with new Kapton tape. The final is to remove the overwind and fit a tripler to generate the EHT, not ideal as it changes the TV from its original configuration but it does work.
Hi crusty,
Thanks for your response in turn. Yes, you are right, I was vague previously and so I’ll try to tell you as much as I know so far. Well, it has been used a lot more recently than 40 to 50 years but obviously not as an operating television set due to the analogue to digital switchover. It was checked by a qualified technician a couple of years ago but nothing since then so I’m naturally very cautious. I certainly don’t intend to use it regularly as it is more of a showpiece than anything else. In addition to this, I adore the set due to it’s totally original condition and so I don’t intend to convert it in any way for future use as a functioning television receiver. I have been told by a former television technician that I know, to power it up for a very short period of time every once in a while and to avoid giving it a sudden surge of power after a few years of sitting without any. To cut a long story short, I will not be putting it to any significant amount of use by any means so don’t worry about that. Thanks again for getting back to me, my friend. 🙂
Kind regards,
Cameron.