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CTV Ferguson 3755 Movie Star - TX9 (PC1044 main chassis)

 
First Light
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Posts: 23

I am trying to repair one of these portable colour TVs.

I have a copy of the RTVS service data for the T.C.E TX9 Chassis (PC1001 and PC1040 main board versions). Also the RTVS book for 1982 to 1983 models, which covers the series 1044 main board chopper power supply.

I have fixed a couple of faults so far and the main chopper power supply outputs are now present. The 115V dc output is a bit high at close to 120V. The 18V output was initially missing, but having replaced C147 it now measures OK.

There are no signs of sound or vision as yet.

The supply to IC54 is present and so I was next going to proceed to check the signal from its output through TR67 to the line output stage. (As described in the RTVS service data) There is a slight complication however, in that there seems to have been some changes in this area of the PC1044 main board, when compared to the earlier PC1001/PC1040 versions for which I have the circuits and service data.

Can anyone help me to obtain a copy of the correct circuit diagram and service data for the PC1044 version of the TX9 chassis?

Any suggestions for further fault finding of this set would also be welcome.

Regards,

Richard

 

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Topic starter Posted : 19/02/2022 10:26 pm
crustytv
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Posts: 10839

Hi Richard,

I'm a little confused, (that's not hard to do these days) I thought the Fergy 3755 was the first, 1st gen 14" TX9 offering from Thorn, and as such had the Thyristor PSU. Did They release the 3755 again, but with the PC1044?

I thought the TX9 came in three waves, the 1st being the chassis as above, then the second version which escapes me, I think it had something to do with the decoder being changes. The final TX9 being PC1044 with switch mode power supply and another new decoder.

Must admit, I've not even started to repair any of my TX series sets yet, so fully expect I've got this all wrong. I expect, John, Jim (ex Thorn) or Baz will be along to put me right.

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Posted : 19/02/2022 11:28 pm
crustytv
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I have the Thorn TX9 manual, but it only covered the 1001 and 1040. Jim just sent me the 1044 supplement, which will be uploaded to the library in due course. But for now, here's the 1044 cct

pc1044

Edit:

Ah-ha, the three Tx9 versions, I wasn't wrong. I also see that the 1044 can be substituted into the earlier models, I wonder if that is how your 3755 ended up with a PC1044?

TX9 versions

 

 

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Posted : 20/02/2022 12:37 pm
First Light
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Busy V-Ratter Registered
Posts: 23

Hi Chris,

Thanks for your reply.

I am quite a novice as regards television fault finding, with no prior knowledge of these particular sets.

I have owned this Ferguson 14" Colour Portable from new, but until a few days ago it hadn't been powered up for many years.

I was initially unaware of the different versions of the chassis and purchased the RTVS service data for the T.C.E TX9 Chassis (PC1001 and PC1040 versions).

The full model number of my set is 3755G + AK with serial number 103112 and according to the silk screening on the main chassis PCB it is type 1044B.  

Luckily I also had a copy of the RTVS book covering 1982-83 models, which includes details of the revised power supply circuitry used on the series 1044 main panel. 

What is confusing me now is that some other changes seem to have been made between the PC1001/PC1040 main panel and the PC1044B version fitted in my set, i.e. changes other than within the power supply section. If anyone can shed any light on these differences and/or share a circuit diagram specific to the PC1044 main panel that would be very helpful. 

 

Regards,

Richard

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Topic starter Posted : 20/02/2022 1:08 pm
crustytv
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Vrat Founder Admin
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Curious, I'll have to bow out and leave it to the ex Thorn boys to further assist.

As far as I can tell, it appears on the 1044, the signal and timebase circuits remained as described in section 'E' of the TX9 service manual, which is in the data library. The exception being the SAWF filter panel, which removed the previous manual pre-set pot, for automatic AGC. Subsequently, Thorn did release issue 3 of the fold-out circuit diagram to cater for this, perhaps that has what you need. However, I only have issue 1 and issue 2.

20220220 125549
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Posted : 20/02/2022 2:06 pm
Jayceebee
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I can’t speak for the Ferguson models but their rental cousins 5170 and 5171 had quite a long production run so possibly did see some fitted with the PC1044. As you have discovered apart from the total redesign of the PSU  there are changes to the line drive stage. The original had a dirty supply tapped off the emitter of VT67 to get the line osc/drive going in IC54, once the line stage was running a clean supply took over from the 12v regulator fed from the LOPT.

Back to your problem, from the information Chris and Jim have provided you should be able to solve this. First, see what voltage you have on the collector of TR67 and pin 4 of IC54. Also give the line hold pot RV206 and RV214 a turn from end to end a couple of times and set them mid point. They can develop dead spots which can cause odd effects.

BTW, have a look on the back cover from a small label something like G82-25, this will date it’s production. G is Gosport E is Enfield, 82 is the year but may be a single digit and 25 will be the week. Good luck.

 

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Posted : 20/02/2022 2:19 pm
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jcdaze
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I've looked for my copy of the issue 3 circuit diagram but not found it yet, I know I have it somewhere but it may take some time to find it. I see the model number is followed by +AK and I probably should know what it means but I can't remember. Has the set got a special interface maybe such as an AV input? I kind of remember some modded monitor versions of the TX9.

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Posted : 20/02/2022 2:49 pm
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First Light
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Busy V-Ratter Registered
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Thanks everyone for the replies and the info.

The small label on the rear cover says G2-41. So presumably that means it dates from 1982?

As far as I am aware the set doesn't have a special interface.

An update on my fault finding. The voltage at pin 4 of IC54 measured 11.8V which is good, but the waveforms at the base and collector of TR67 didn't seem right. Further checks have revealed that RV206 is open circuit. I don't have a suitable replacement among my spares, so I have ordered one. I'll report back once this pot has been changed.

 

Regards,

Richard  

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Topic starter Posted : 20/02/2022 11:00 pm
Red_to_Black
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Basically the TX9 came in three versions, the MK1 PC1001 used the Thyristor power supply and an NEC colour decoder chip UPC1365, transistors were designated VTXX and diodes designated WXX, the MK2 PC1040 also used the same Thyristor PSU as the MK1 but with all modifications in production of the MK1 implemented, it used a different colour decoder IC the Philips TDA3560, this was to cater for teletext as this IC had RGB inputs which the NEC UPC1365 didn't. The Mk2 also designated transistors as TRXX, and diodes as DXX.

The Mk3 PC1044 used a redesigned chopper power supply using the popular TDA4600 chip, it still used the same colour decoder IC as the MK2, This chopper PSU also catered for standby operation which the earlier Thyristor version couldn't do, transistors and diodes were designated the same as the MK2.

There were of course other subtle changes throughout the chassis, some of which were running production changes along the way via the MK2, and some which will have been specific to the MK3.

 

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Posted : 20/02/2022 11:11 pm
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