Now you've got me worried...... I've seen that evil glint in your eye before. I take it I'm about to have an education delving into ultrasonic remote receivers. 😲
Feeding in colour-bar, further reveals servicing work required. I'll have a look into this today and see what the manual has to say about setting up the decoder. Then I'll look at the ultrasonic fault.
Feeding in colour-bar, further reveals servicing work required. I'll have a look into this today and see what the manual has to say about setting up the decoder. Then I'll look at the ultrasonic fault.
Those "bright-ups" seem to be affecting the blue channel.
What a result ! I have followed this thread with great interest! I think I only saw a couple of 4000 sets 'back in the day'. I avoided them when they appeared in the disposal places as a lot were incomplete and had panels unplugged presumably swapped. I had been "warned" about thick film problems and the complexity, they had a reputation for being a bit unreliable and generally didn't seem to be liked outside of the rental firms that had them. Probably wrong because a lot of engineers didn't like the 3/3500 and the 9000 which I had loads of and got on well with.
……generally didn't seem to be liked outside of the rental firms that had them
Hi Rich, they weren’t even liked in the Thorn Rental outlets at the time either. Back in the day they seemed horrendously complex but I look at the circuit now and compared to what Thomson foisted upon us I think what was all the fuss about?
The most intimidating part now is the remote control. Long time since I worked on TTL J-K flip flops, latches, counters and the like, all forgotten. At least the board can be worked on out of the set with just mains supply and a scope, be interesting to see what Chris finds and if I can dredge it up from the depths of the old grey matter but I think most of it has permanently gone.
With no experience of ultrasonic remote control, would I be right in an assumption that the frequencies, as listed below in the transmitter, are absolute? The reason I ask is that I decided to place the remote in front of my frequency counter, and the function frequencies appear off. Some not by much, others by a fair amount, but if they need to be absolute, then perhaps the receiver is OK, and it's the remote at fault.
For example; channel change is listed as 33.6kHz, I'm sending 33.3kHz. Colour down is listed as 44.4kHz I'm sending 40.0kHz. Brightness down is listed as 40.8kHz, I'm sending 39.8kHz.
Now, it could be that placing a probe in front of the counter unit is not good enough. I've not done this before on ultrasonic remotes, but have in the past when determining line speed of an old 405 TV. I assume this test for the remote is a valid test. I thought it prudent to know the transmitter is working as it should, before assuming the receiver is at fault, and all that entails with its diagnosis. It would appear the transmitter is off, hence why nothing is happening at the TV.
The manual states that you should not go adjusting the master oscillator via L951/L952 or C954 in the transmitter, as it was carefully set in production. Unless it is possible to monitor the output frequencies (33.5kHz - 44.5kHz) with suitable test equipment. I would think my counter does fall into the category of suitable, unless folk feel otherwise.
However, even if it is suitable, how do you set it up the transmitter frequencies? Is it a case of aligning one, then they all fall into line, or is it a case of adjusting each one?
The manual does go into great detail diagnosing the receiver end, but it does assume the transmitter is blameless.
There is some wiggle room with the frequencies but not a lot I seem to remember. If the remote is slightly off frequency then I would expect to see some buttons doing the wrong function. The first checks I would do is on the amplifier stages IC451A/B by checking the output from the Schmitt trigger IC552B pin6 while pressing any button. If you do have pulses here then the master oscillator probably will need adjustment, I would say the equipment you are using is more than adequate and probably much more accurate than we had by in the day.
However, even if it is suitable, how do you set it up the transmitter frequencies? Is it a case of aligning one, then they all fall into line, or is it a case of adjusting each one?
Sorry, I forgot to answer the above question. The function to use to setup the master oscillator is colour down as no parallel capacitor is added, it only switches battery power.
I wouldn't worry too much about spot on frequencies at the moment. As long as the tx is transmitting then it is possible to work on the rx up to point and I would expect some functions to work even as it stands(as Jayceebee says). The microphone in picking up all sorts of signals and the circuit sometimes used to get confused and decode whistling birds and rattling keys etc as a command. I have the same U701 transmitter and it does transmit and if it comes to it I can check how accurate the frequecies are.
This morning I sorted out greyscale & the minor convergence problems. What a wonderful unit the hand-held control is, static, blue lat & dynamic all on one unit.
Before & After
I'm left with a curious fault over on the left-side, I'm not sure the cause of. I tried adjusting L113, but that did nothing.
It may be an action with the camera but there appears to be a lot of cross colour in the frequency gratings and the colour bars at the top appear to have Hanover bars.
Does altering the line hold shift the odd effects the left hand side, just wonder if it’s a timing problem.
Hi Frank, adjusting line shift does not change the left side fault. If it were not for this problem, I think it's giving a fairly decent picture considering it's running on 98%+ original components.
I thought the confetti in the bottom (4.0 /4.5) gratings was normal, I've seen that on countless TVs, just look through my erpair blogs, Baird, RBM, Thorn etc, all have confetti. Happy to standard corrected if that's not the case.
It's this colour fold-over on the left (incorrect term, but I don't know how else to describe it) that's got me at the moment.
![20220731 224552[1]](https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/884/12369-202207312245521.jpg "20220731 224552[1]")
