Dynatron CTV22A

[pastyboy]

Hi all you pop pickers

Purchased the above set from a junk shop this weekend and as a little teaser does anyone know the chassis fitted (set is well and truly chokked in my waggon and won't be unloading until tomorrow) Its a delta tube and has a cracker of a ultrasonic remote (to coin one of Mike Bennetts favourite embellishment terms) the size of a brick.

I am guessing it might be a G8 or a decca or a pye, it has a VCR button on the back along with various inputs. I place it around 1973 - 76 as would have thought much later a PIL tube would have been fitted..Matey in the shop was keen to get his extension lead out to it but I said don't bother in the damp the best it will do is fizz and arc over !

Also a bush tv62 and a same era dynatron table top set came across so a productive but expensive weekend in the west country. Shame the Wadworths real ale was in top form too !

[dazzlevision]

Hello,

Your Dynatron CTV22 will have the Pye 731 series solid state chassis fitted, coupled to an imported Philips ultrasonic remote control system. It's uses a Philips/Mullard 110 degree, delta gun CRT. The (Pye) printed circuit boards are mounted vertically and "fan out" either side of the CRT's neck.

Regards,

Dazzlevision

[1955APREN]

HI
Just a couple of common faults
1 Thick film resistor unit on video board one colour missing
or very bright screen

2 Metal covered resistor mounted by mains dropper resistor
30 watt i think causes dead set
Regards Derrick

[Welsh Anorak]

Hi
Not my favourite chassis, probably due to the fact that back in the day I was delivering a Pye 26" version when, unknown to me, the mains plug got stuck in the car's bumper. Suddenly I'm holding fresh air and there's a Pye in kit form on the ground, all witnessed by the proud owner!
In addition to the thick film problems the IF unit was naughty and usually needed soldering up on the 'through board' links. The decoder ICs failed quite regularly as well. The tripler failed quite often and was harder to change than I would have liked. I think there were a couple of those green tubular tuning capacitors familiar to G8 enthusiasts in the LOP stage.
The PSU was pretty much like the G8's design but seemed very prone to HT flutter.
The picture quality was better than the 205 it replaced, though that's not saying much.

[FERNSEH]

In the seventies I had a small number of the Ekco branded version of the 731 on rental. Model CT826 seems to come to mind. The customers liked the slim cabinet but I must agree with Glyn these sets weren't all that good really. Reliability wasn't the best and the picture quality was only so so.
Nevertheless, I did get the full service life out of them.
DFWB.

[Nuvistor]

Agree that the 731 was not that reliable, they produced the 725, I think, chassis with a 90 degree CRT shortly after, think I have timing correct. Very similar electronics but the scanning/power supply requirements were reduced and that for me was much more reliable. The signal stages did not give me that much trouble, it was the scanning/ PSU.
Something in the back of my mind about dry joints in the IF stage with double sided print feed throughs or was that the G11?

I never found any of the U.K. sets made 1973- onwards that good on reliability.

Frank

[FERNSEH]

731 chassis: It was the IF module that was prone to dry joints. The firm LEDCO made a replacement module which used a SWAF bandpass shaping filter. In due course nearly all my 731 and 725 sets finished up with this unit.

LEDCO along with many other things made an all transistor replacement for the Pye CT205 CDA board.

DFWB.

[Nuvistor]

I did not see the replacements for either PCB but I recall the name LEDCO. After my time in the trade, probably saw the name in the Television magazine.

Frank

[Philips210]

Hi

Agreed the 725 was better than the 731 for reliability. I have to admit they weren't too bad for servicing. ISTR the Pressac connectors on the various panels were of the same type as used in the Mullard VM6101 teletext decoders.

As has been said, the IF module in the 725/731 produced a weird array of faults, due to solder joint problems. I think this was mainly due to the ceramic plate capacitors making a poor connection in the solder joint. There's an excellent servicing article on these sets by Mike Phelan in 'Television' magazine September to November 1979.

One crucial thing to watch out for is C563 (0.1uF early sets, 0.22uF later sets) connected to the LOPTx overwind. Failure of this component can cause a chain reaction of failure of the tripler, LOPTx and line output transistor. It's important that the voltage rating of C563 is 1250V.

Regards
Symon

[pastyboy]

All noted and understood it looks like a 1974 set if indeed the upside down stamp is the date, looks tidy enough inside and now she is on a wooden dolly I can move her around the yard ! hopefully get on the case today !

[Restoration73]

IIRC that chassis was designated 733. Later ones had the quick heat tube and a changed
tube pcb, might have been called 743. Nice cabinet.

[FERNSEH]

I remember a 741 chassis.

DFWB.

[Nuvistor]

Was the 30AX a quick heat CRT? so much I have forgotten.

Frank

[dazzlevision]

If you are referring to this Pye 731 series chassis, then it wasn't a 30AX type, but it was 110 degree scanning angle. The 30AX came a few years later, with the 20AX in between.

[Nuvistor]

Yes realise the 731 was a 110 degree CRT, it was post#11 that made me put quick heat and 30AX together in my mind but I just cannot remember if it is correct.
The 20AX and 30AX had the CRT and scan coils as one Assy and removed a lot of convergence problems, again I think that's correct.

[FERNSEH]

Early 731 receivers used the A66-140X CRT and later on the chassis was modified to accept the quick warm-up A66-410X.
22" models used the A56-140X, later models were fitted with the A56-410X.
The quick warm-up tubes had a reduced heater current.

We discussed some time ago about the existence of a quick warm-up version of the 90 degree A56-120X.

DFWB.

[pastyboy]

hi all, yes Chris Crusty says its a 733 and looking at the psu cct of the 731 its slightly different.

Dropper section 56r was OC a ww hung in there still had no effect. I had previously checked quite a few PSU components.

The thyristor is OK so I took a chance and fired the set up with the over volts circuit disabled by taking one end of r903 out.

The set fires up but the frame is bouncing around possibly supply voltage yo-yoing ? but it could be a frame fault or just the hold preset needs a turn.

Picture seems grainy - low tuner or IF gain but colour and sound all there.

Get back to the set in due course.

185v rail is 190v so

[Philips210]

Originally Posted by Nuvistor

Yes realise the 731 was a 110 degree CRT, it was post#11 that made me put quick heat and 30AX together in my mind but I just cannot remember if it is correct.
The 20AX and 30AX had the CRT and scan coils as one Assy and removed a lot of convergence problems, again I think that's correct.

Hi Frank.

Going OT from the 731 series, and to answer the query re quick heat tubes, the early versions of the 20AX (500X) had the slow heat cathodes whereas later versions designated 510X had the quick heat cathodes. The 20AX series required convergence tolerance controls for dynamic correction.

I believe the later 30AX (540X) all had quick heat cathodes. The 30AX had no dynamic correction as it wasn't necessary.

Regards
Symon.

[FERNSEH]

As used in the late production 731 receivers. The quick warm up CRT.

http://www.radiomuseum.org/tubes/tube_a66-410x.html

The original delta gun 110 degree CRT.

http://www.radiomuseum.org/tubes/tube_a66-140x.html

Note the reduction of heater current in the later tube.

It's all coming back. Didn't the later 110 degree CRT sets use a different channel selector button assembly? The early production sets used the channel selector which had a tuning scale for each button.

DFWB.

[Nuvistor]

Thanks, some of it coming back, not using the knowledge for going on forty years I forget so much, other things take over.
I do now remember the 140X and 410X heater variations but if some one had asked I would no idea.
Frank