Introduction

This TV is a recent addition and is a manufacturer up until now, not represented in the museum collection, in fact I have also acquired another ITT TV but more on that in another blog. I’ve no idea of the model number of this TV as the original rear  cover sticker is missing. If anyone out there recognises this TV please drop a comment down below.

The chassis employed in this TV comprises a horizontally mounted power board (CVC-823) and a vertically mounted signals board (CVC-824T), the “T “meaning it has the tint option. The chassis is intended for use with 20″ & 22” PIL (Precision In Line) picture tubes fitted with integral scan yoke and quick vision cathodes giving display of picture within approximately five seconds from switch on. The TV had options for either mechanical or infra-red control units.

Technical Specification

Power supply : AC only SMPSU
Consumption: 55W
CRT: 90-degree PIL 20″ 510-VSB-22-TC-01
09-degree PIL 22″ 560-EGB-22-TC-01

Frequency Range: UHF bands IV and V 21-68

Chassis

The chassis as can be seen from the below photos, consists of two sections, a horizontally mounted power board carrying power supply, timebases and eht stages;  and a vertically mounted signals board carrying the HF module, interface module and colour decoder. Both boards slide into plastic channels fitted and the top and base of the cabinet. The power board is held secure by two plastic latches and the signals board is secured by one screw fitted at the bottom rear end of the board.

Boards

CVC823 –       Main board with PSU and timebases
CVC824-        Signals
CMR800 R.I/I.F/A.F
CMN800 Interface Board
CMD800/T decoder with tint

CMB802-       CRT Base
CMC77/2&3- Control unit
VCA45/1-        8-way push button control unit

Condition

Overall the condition of the TV is  very good, especially considering it is 43-years old.  The cabinet is in good shape without any nasty dings/dents  or missing veneer. All the controls are present and function. Inside the set was coated in a this dry layer of dust, which when touched leaves you covered in a black soot like substance. Before anything else is done, the TV shall be hoovered and then the CRT test to determine if any time is worth investing into the restoration/repair of the set.

Some initial photos.

As can be seen below this is the only sticker on the back, is this the model? If so seems rather contrary to the normal ITT numbering system.

Next, test the CRT emissions

To decide whether the repair is viable, the CRT cathode emissions needed to be observed. There’s no point investing time and materials only to find the CRT is beyond use.

First observations show the blue cathode appearing to be low, however we know that a CRT not run for many years will improve.  So I upped the heater from 6.4V to 7.4V and left it to cook any crude from the emissive layers. This did the trick, 30-mins later the blue gun having recovered itself quite considerably. The repair is viable and will continue.

As can bee seen below, Blue emission is borderline, Green being the best and Red OK-ish.

Upped the heater volts to around 7.4V, and left cooking the cathodes for over 30-min – 40-mins.

Red improved, Green improved and finally Blue also improved.

Power Application update with initial observed faults

Power applied and test signal supplied to the TV, and it came up with a snowy raster. I then tuned the tuner to the test signal to be greeted with vertical unlocked.

1. No matter how much adjusting of the skeleton preset would give vertical lock. The best I could achieve was a VERY slow roll. I left the TV running for a while and then found I could get a solid lock, although this would go nuts again when the channel was tuned, and cured with a tap to the cabinet. No doubt there will be some out of tolerance component in the vertical frequency circuit, not least of which will be the Skeleton preset and dry joints.
2. No sound whatsoever
3. Dry joints
4. Video drive RGB drives and A1’s need set up, as red is dominant.

Edit: add to that 5. After a while the brightness increases quite significantly, with brightness control becoming ineffective. Power off and back on a few seconds later, the problem clears.

Next steps, consult service manual to study circuit and tackle the initial observed faults, more to follow.

Update 26th May 2025

I’ve been reliably informed by a former TV trade engineer who had this chassis cross his bench on more than one occasion, that it is highly probably the combined CMR800 module is the cause of all my troubles listed above. I quote:-

@The_Teleman said:

The no sound, lack of frame sync etc are very likely to be the metal tuner unit. The ITT one is an odd one, certainly as it contains the tuner, the I.F, the sync separator and the sound output to name but a few things. The soldering on the PCB was always a problem. You need to remove the covers, then you will see where the pin-outs are, and in-between them are the earthing points the all too frequently go dry-jointed. Also check around the edge of the can too, as the soldering here was always a problem.

As there appears to be zero documented examples of this TV out on the web, I will fully document the chassis for Radios-TV. I’ve scanned the relevant section of the service manual.

Update 29th May 2025

Removed the signals frame giving easier access to the video output/decoder and to be able to remove the CMR800 module. Inspecting the three RGB output transistors reveals base emitter and collector pads are dry jointed. Rocking them clearly showing intermittent connection, this will account for the poor colour.

The CMR800 module was relatively simple to remove from the frame, a single screw remove allows the unit to be pushed upwards to the outer frame dislodging the pins from they lock position. The front and rear can covers were then carefully prised off revealing the component and print side. Just for clarity the sync separator as mentioned above, is not in the can, the sync sep is IC711 TDA9503 which is located on the mainboard.

Within the CMR800 can are TDA4420, SL1430 & TDA1035T

TDA4420 : Vision IF amp, Vision demod, AGC
SL1430: Fixed gain TV I.F Preamplifier
SW153A: SAW filter
TDA1035T:I.F. amplifier, Demodulator, Electronic volume control, Output amplifier

I note in the audio stage there is one of those unreliable thick film units, I hope that is not the cause of my no sound.

Next three photos show the video output transistors all dry-jointed

Update 13th June 2025

I reflowed all the dry joints in the CMR800 and on the video/decoder PCB,  especially the RGB outputs, them squirted servisol in the line timebase pre-sets. All OK now, not one single component has been changed.

The End

Watch out for the next patient on the bench, the much earlier CD662 see here

p.s.

If you’re thinking the testcard is not filling the screen, that’s nothing to do with the set. It’s due to my Raspberry Pi test card gen I rigged up in the garage, I need to edit the config file to set the correct overscan.