CTV Oct 1988 20" Granada C51EZ4 (Salora 20L30) with Teletext

I think my brother had an L-chassis set, following on from the K-series my parents owned (a 24K77, which were also sold as Hitachi sets).

I have one of those exact remotes Chris, not sure if you are aware of this or not but the remote can be used to generate a secret code that will alow you access to the sets internal Eeprom for reprogramming, on my remote I fitted an external button to generate the code. 

I have one of those exact remotes Chris, not sure if you are aware of this or not but the remote can be used to generate a secret code that will alow you access to the sets internal Eeprom for reprogramming, on my remote I fitted an external button to generate the code. 

Hi Michael, no, I was not aware of that at all, this era of TV is way out of my area of experience. Amazingly, I too had one of these remotes in my box of spare remotes. I often wondered what TV it might be for and had hoped it might function on my other 10-years earlier Salora, the 1979 Salora 1F4.

Hi Chris.

Glad it arrived in one piece. Just a shame it doesn't B***dy work now. Typical, I had it on most days for a few hours and it never skipped a beat. 

I didn't have to do anything electrically to it, In true yampy187 fashion, I Just plugged it in and away it went. Just looking at the photos, Id change that white Rifa cap in the primary. They are also prone to spewing smoke out, just like the older resin encased types.

I'd think it would only be a dry joint or a loose connection somewhere causing no sync. Whatever the cause, Its in the right hands now 🙂

Ill be following this thread with great interest!

Jan

I might be wrong about this as I'm looking at a NEI service manual that uses the same micro but the notes I have written here is, if the remote control chip is a SAA1250 then linking pins 15 and 23 for a few seconds will get you into the Eeprom for re programing. 

I may just have found the cause, L502 in the Hoz deflection circuit has a dry joint, whether it is the primary cause remains to be seen.

Extract from a Bush service manual, you would need to get the correct options though for your set, I have a feeling some of these salora  sets could loose the text option and it was a simple matter to flip a bit in the Eeprom to get the text back.

@michael-dranfield It looks like it also has a blank space for SCART/AV inputs. I wonder if these options could be added/enabled in the EEPROM?

Posted by: @crustytv

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I may just have found the cause, L502 in the Hoz deflection circuit has a dry joint, whether it is the primary cause remains to be seen.

Wishful thinking Crusty, it wasn't.

I guess the best place to start now is over at the TDA4505 and scope the hoz outputs. I get to use my new battery combined 100Mhz dual channel scope/Multimeter.

Horizontal Sync TDA4505 (spec sheet)

DC Volume Control/Horizontal Oscillator Start.

The circuit can be used with a DC volume control or with a starting possibility of the
horizontal oscillator. The operation depends on the application. When during switch-on, no current is supplied to Pin 11, this pin will act as volume control. When a current of 6mA is supplied to Pin 11, the volume control is set to a fixed output signal and the IC will generate drive pulses for the horizontal deflection. The main supply of the IC can then be derived from the horizontal deflection.

The video input signal (positive video) is connected to Pin 25. The horizontal synchronisation has two control loops. This has been introduced because a sandcastle pulse had to be generated. An accurate timing of the burst key pulse can be made easily when the oscillator sawtooth is used. Therefore, the phase of this sawtooth must have a fixed relation with respect to the sync pulse. That can only be realised when a second loop is used.

Well, that's told me nothing that I didn't already know the hoz osc is off-frequency, not by much @ 15,63xKhz.

Checking the three relevant pins on the TDA4505, as I say, just confirms no line sync. I wonder if it's the 10K skeleton preset RT103, these have caught me out before. This preset is used for setting the line osc frequency, it's a devil to get at.

Readings:-

Pin 23 hoz osc hold should be at 2.6V I'm at 1.9V (.7V discrepancy, likely due to the lack of sync)

Pin 24 hoz osc should be at 2.5V I'm at 2.9V (.4V discrepancy, likely due to the lack of sync)

pin 27, sandcastle should be at 10V, I'm at 9.9V (OK)

Will the set work with the text board disconnected? I had a Akura (Goldstar) set that had similar symptoms. would run fine with the text board not attached. Which turned out to be dry joints not letting the sync through. 

@crustytv Before diving in too deep remove the ICs on the text board and give them a clean. Sockets can be more unreliable than the chips they hold and give some very weird symptoms.

Posted by: @yampy187

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Will the set work with the text board disconnected?

I guess so, the manual states the Teletext was a Kit module and that all models could be converted in the L-chassis range. It's simple to remove, just two flying ribbon cables connect it to the mother board.

Well, I'm speechless, I would not have suspected the Teletext board, that shows my lack of experience with text sets. Cheers chaps.

Jan, I wonder if the fact you were having trouble getting the TV to switch into text was the indicator of something failing.

I was about to remove the chips from the Teletext board to clean the pins and sockets, when I spotted this.

IC15 the KM4164A-15 (DRAM chip) has pins 13,14,15 & 16 not in circuit. Looks too deliberate rather than a mistake. Why?

Edit:

Anyway, removed and cleaned the three large chips and sockets, reinserted Text board, same fault present.

I haven't seen any of these sets Chris, All the Salora sets I saw were the earlier models. Even those could be a challenge at times throwing up the occasional fault that defied logic and took some chasing. It seems strange that it appears to have more than one fault. Sync, video and focus?  I suppose the lack of sync could be connected to the video fault but why would that affect the focus? 

As it worked before it was transported I would look for drys or hairlines around the connections to the LOPT maybe on the earths? As you know these can be hard to spot if it is around the circular print landing where the pin goes through the panel. I remember having intermittent faults on something, maybe a Panasonic, nothing could be seen but three bits of print would go open circuit intermittently depending on temp and flexing the LOPT. This took a bit of finding as they wouldn't all play up at the same time. In the end to prove it beyond doubt I metered each track while flexing the board.

Can you check the focus volts and see if it is adjustable with the pot. I see it is a thickfilm focus and A1 pot, has it gone rusty inside or has a connection become loose?  It was common on the KT3/K30 etc for the focus lead to pull the tag off the thick film you had to be careful when cleaning the PCB because if you caught the lead with the paintbrush it didn't take much for the tag to break off.

As to why the chip is inserted like that? No idea, as you say it looks deliberate. My first thoughts were to override or disable a function? 

I'm sure you will sort it! 

Rich.

@crustytv Removing ground, data, column address strobe and one of the data pins seems a very odd thing to do indeed. I'd be inclined to just straighten the pins out and put it back in its socket properly.

I wonder if it's the same text board that's in the K series sets? I might have one of those in the store as I have a K-series chassis from a set I scrapped.

Posted by: @slidertogrid

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I would look for drys or hairlines around the connections to the LOPT maybe on the earths? As you know these can be hard to spot if it is around the circular print landing where the pin goes through the panel. I remember having intermittent faults on something, maybe a Panasonic, nothing could be seen but three bits of print would go open circuit intermittently depending on temp and flexing the LOPT. This took a bit of finding as they wouldn't all play up at the same time. In the end to prove it beyond doubt I metered each track while flexing the board.

Can you check the focus volts and see if it is adjustable with the pot. I see it is a thickfilm focus and A1 pot, has it gone rusty inside or has a connection become loose? 

Hi Rich, I must be missing your train of thought, so please forgive me. I fail to see/understand how the points you suggest to check are in any way related to the Teletext board fault?

If, as you suggest, the points you raise above were indeed related to the cause of sync loss, why then does the TV work perfectly fine without the Teletext module installed?

This can be witnessed here. The TV was left running all evening yesterday, without any problem, putting the Teletext module back in, caused the fault to return. This, I suggest, confirms without a shadow of doubt, the fault lies within the Teletext module and not on the mainboard. A bit of research over on UKVRRR revealed some ex Salora engineers stating the Teletext module faults across the range are notorious for causing ratehr bizarre fault conditions.

Observation

An observation I've made,with this fault may or may not give a clue to the more educated among us, is as follows:-

Teletext module installed

Upon powering up, the TV is in standby mode, then press 1 on the remote to bring it out of this condition. The resultant raster is very dim, so I have to adjust the brightness up, to assist with seeing and tuning in the signal (Test card F and music). When I get on signal sound is perfect but visually all I get on the raster is the sync and flashing fault, as shown in post #1.

Turn TV off, remove Teletext module.

Now with the Teletext board removed, when I power up and press 1 on the remote to come out of standby, I'm instantly greeted with a nice clear, visible snowy raster, unlike when the Teletext module is installed. Tuning into the signal (Test card F and music) results in perfect sound and a perfect test card. 

My monkey brain is thinking this is a significant clue, could it be related to blanking? Don't all laugh, I know I'm out of my depth here, just trying my best to get my head around how the Teletext cct is impacting the signal path, thereby causing the condition I've just described.

Also, not helping me is the L-Chassis manual I have appears a September 1986 edition, and the teletext module in my TV is a few versions newer than the one shown in the manual. As such, I'm not even sure on the date of this TV being 88, quite possibly it might be earlier than 86.