Dynatron CTV9 - Pye hybrid chassis stock faults

[Hunts smoothing bomb]

Hi all,

I need some advice on a CTV. There is a Dynatron CTV9 in a lovely ornate cabinet for sale I am quite interested in getting.

The questions I have are, Is the tube in the CTV9 short lived? because I found a nearly identical set on Mike Bennet's site but a CTV5 and he says they are fitted with short lived tubes.

Also are these sets fairly reliable as I am just starting to get into the complex minefield of colour tv and don't want to be plagued with lots of complex faults. What chassis does it use? a Pye something?

The set is described as not working; I was wondering if there are any common faults with this model?
Please tell if this is a good buy, or if it should be avoided at all costs!

Thanks all,

Lee

[ScreenSaver]

Hi Lee,

The chassis will be a modified version of the Pye 691/693 series. Various tweaks to justify the Dynatron branding, but basically mostly the same.

All large screen delta gun crt's have to work hard, given the amount of energy absorbed by the shadowmask that never makes it to the phosphor, so finding a good original one nowadays, in my experience, is a bit of a lottery. You have to hope for a set that wasn't used very much (being a Dynatron it may have been in a posh room not used very often), or has had a replacement crt (re-gun or new) fitted at some point towards the, or in, the early eighties (again, being a Dynatron the owner may not have been short of the cash to do this). You never know until you see the picture, even tube testers don't tell the full story.

Not especially unreliable I think, except for the notorious 'fried crisp n dry' CDA boards!

ScreenSaver

[Mike Phelan]

Lee
A few stock faults for you:

• PCL84s running into grid current - change 2m2 grid leaks to 680k
• Clean underside of edges of print on CDA panel.
• Intermittent loss of colour - 2 x 4700pf Suflex caps in reference osc.
• Line osc stopped and PY & PY glowing - o/c resistor in series with line hold control.
• Striations on LH of raster - 1k5 across linearity coil o/c
• No line sync - 47k 1w from LOPT to flywheel sync cct.
• Weak line and field sync - contrast control gone high.
• Ripple on raster lines on wired LTB chassis - earth line osc coil can.
• Intercarrier buzz - adjust core in FM slope detector coil on IF strip.

Weak points are noisy chroma on poor signals and LOPT and tripler failure.
HTH

[Focus Diode]

To add to Mike's list above: If R227 (100K) is burnt C224 (0.1uF) will probably be found s/c. Fit one above 1KV if you have one.

I strongly recommend Mike's suggestion to replace the three PCL84 grid leak resistors with 680K ones and would go as far to say this is essential when handling these sets. I once had a case of fading red over a period with an overheating red PCL84. Changing the resistors to 680K cured the fault without having to replace the affected PCL84, with no further CDA panel problems.

Keep us upto date with the set Lee.
Cheers,
Brian

[Hunts smoothing bomb]

Thanks for all the info guys,
These sets don't sound too bad at all, like you say, it's just a gamble on the tube and LOPT as the other faults sound like relatively normal cap/resistor faults.

What year were these chassis produced?
I have radio & television servicing volumes upto 1969-70

Regards
Lee

[Focus Diode]

The Pye hybrid series in its variations were made between 1967 to 1975(!). Obviously later versions had their differences namely single std, EHT tripler in place of the GY501/PD500 "smokestack" and the re-designed PCB PSU/LTB panel. This is compatible with the earlier single std wired version but sometimes the edge connectors don't fit correctly.

The LOPT is prone to trouble, but thankfully later versions are more reliable.

A feature dating to the earliest dual standard version is the solid state frame timebase panel, the small one between the CDA and LTB/PSU one.
A word of caution is applicable to all models in that these sets are LIVE with the receiver plugged into the mains. Direct AC goes to the 2.5A anti surge fuse on the PSU panel (top on the PCB panel version)

The date of manufactuer can usually be found on the CRT degaussing shield.

Cheers,
Brian

[ScreenSaver]

Hi Lee,

I think the one you're looking at buying is a later version with PCB line output section and tripler etc. I'd put it at about 1973 if that helps.

ScreenSaver

[Hybrid tellies]

Looks like everyone has mentioned all the ailments effecting this chassis. The first company I worked for was a main Dynatron dealer in Bath so we saw loads of these.

Overall they were not too bad, but did not compare well with ITT or Decca for picture quality, reliability or ease of servicing.

There is another thing to watch out for; if you remove the line output/power supply on refittting it make sure you fit the EHT lead firmly into the focus unit. If you don't you could have a fire on your hands!

[Paul_RK]

The CTV9's entry in R+TVS is in the 1973-4 volume, but consists only of a little under a page of production changes to the Pye 691 and 693 chassis, themselves covered in the '71-2 and '72-3 volumes.

Paul

[Mikey405]

Hi Lee.

When I said the tube was "Short Lived", I meant that not really many sets used that tube and it wasn't made for very long. It was the push-through version of the 25" tube. (A63-120X)

Go for the set though Lee - They're absolutely cracking sets and very easy to fix.

Mike.

[Focus Diode]

Indeed go for the set Lee, as Mike says. All above contributors know these sets well so help isn't far away!

Good Luck!
Brian

[dazzlevision]

Hi,

Looking at the "well known Internet auction website" picture of the Dynatron CTV9, the set has a Pye Group 697 chassis, with a printed circuit line timebase and power board, together with varicap diode tuning. The basic 697 design was modified slightly to include a tint control, low-level audio output and wired remote control.

Unfortunately, the CDA panel and to a lesser extent, the line/power panel suffer from overheating of the PCB material, causing it to darken, conduct and crack/disintegrate. A solid-state version of the CDA panel was available at one time (not from Pye/Philips) or a solid state PL802. Neither of these solid state items worked as well, in my opinion.

I used to fit "stand-off" power resistors and B9A valveholders to the CDA panel, which kept it a lot cooler! There are several power resistors and two thermistors (VA1104 and VA1026) on the line/power panel which should also be stood off.

You'll find the set much more reliable then, together with replacement polypropylene 470nF 1kV boost and 100nF 1kV CRT A1 supply decoupling capacitors.

Also watch out for a leaking HT smoothing capacitor "can" (200+300 or 300+300 uF - on the line/power "chassis".

If the set has any black cased "CALLINS" branded electrolytics - change them all!! There is also a 12.5uF 50V reversible electrolytic on the control panel tagstrip, which can give trouble (brightness faults).

Have a look at the line output transformer. If there is no insulating ring between the EHT tripler feed overwinding pulse output and the transformer ferrite core, I would fit thicker sleeving to the wire and increase the spacing. The early 697 LOPTs suffered from arcing at this point, leading to LOPT and tripler failure - a widespread fault! Replacement genuine Pye (CES/Philips Service) LOPTs were modified to avoid this. The sleeves were green silicone rubber/polychloroprene types.

The small 200Ohm (? - memory!) pot on the field panel goes intermittent and can cause slow flyback with Teletext twinkling lines at the top of the picture. This should be replaced/cleaned and set up as per the service manual.

Finally, there is a small preset wirewound 40 Ohm pot on the convergence panel. This usually goes intermittent and causes North-South pincushion distortion.

The CRT is probably a Mullard A66-120X (or A67-120X) 26" "supersquare" type.

Good luck!

Dazzlevision

[Focus Diode]

Excellent advice there from Dazzlevision. Another capacitor that should be replaced is the mains filter one, at the on-off switch. Again a replacement should be rated at 1KV or greater.

The original 600V type often went s/c which could damage the PCB at the fuseholder.

Hope the set comes your way!
Cheers,
Brian