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Old 21st Jun 2021, 3:07 pm   #1
mark pirate
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Default Bush BTV183DVD/A frame collapse

This set has not been used for a few years, on power up it all seemed fine, but then the picture became jerky & lost vertical size before just displaying a line across the screen.

I tried it a few days later, and got a repeat performance, I have checked the larger caps in the frame section, both tested fine for both value & ESR, but were subbed out anyway, but same problem.
The frame output chip is a TDA 8174A, this shows no sign of damage or overheating.

The set is made by orion and has a VHS & DVD player built in, so I think worth repairing, any ideas to what could be causing problem?


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Old 21st Jun 2021, 3:29 pm   #2
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Default Re: Bush BTV183DVD/A frame collapse

Have you checked for dry joints around the LOPT etc? The frame derives it power supply from a sub supply off the LOPT, and dry's were common on these and similar sets.

Otherwise, I would replace the output IC as the next step; could be overheating and shutting down.
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Old 21st Jun 2021, 3:33 pm   #3
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Default Re: Bush BTV183DVD/A frame collapse

Well, the obvious is a dry joint on the IC or the feed from the LOPTx but I'm sure you've checked that. If possible see if you are able to measure the voltages to the IC under fault conditions- you may well need to attach temporary test points wires to do that.
Then I'd change the IC - and if it doesn't work panic! Freezer and a hairdryer may be your friends here. ISTR a green capacitor in the frame generation circuit giving this fault on an Orion chassis back in the day, but only once.

Post crossed - great minds?
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Old 21st Jun 2021, 3:53 pm   #4
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Default Re: Bush BTV183DVD/A frame collapse

No dry joints that I can see, but reflowed both the LOPT & O/P chip.
The set was working perfectly prior to being unused for a few years, hence why I was thinking it could be capacitor failure.


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Old 21st Jun 2021, 4:03 pm   #5
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Default Re: Bush BTV183DVD/A frame collapse

Resistor going open circuit as it warms up?! If you get really stuck I’ve got the entire guts of one of these knocking about in storage! I was given 3 of them, one had obviously taken a tumble (or been thrown across the room because a DVD got stuck in it!) and the tube was smashed, it did work with a replacement tube, but I was thinning down during a house move so I gutted it and binned the case, and now it takes up more room than it did when it was complete! Don’t know when I’ll get to the lock up, it’s in Daventry, over 100 miles away! I was going to sort it out last year, but we all know what happened...

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Old 21st Jun 2021, 4:11 pm   #6
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Default Re: Bush BTV183DVD/A frame collapse

Quote:
but I was thinning down during a house move so I gutted it and binned the case, and now it takes up more room than it did when it was complete!
I am doing the same, I have already dumped loads of sets, but this one was one I was planning on keeping, I have had a look through my spares, but don't have a replacement chip


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Old 21st Jun 2021, 4:37 pm   #7
MickMcmichael
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Default Re: Bush BTV183DVD/A frame collapse

Hi Mark

If you PM me your address I have a new unused TDA8174A you can have.

Cheers,

Mick.
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Old 21st Jun 2021, 5:23 pm   #8
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Default Re: Bush BTV183DVD/A frame collapse

Many thanks Mick, PM on it's way.


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Old 22nd Jun 2021, 10:15 am   #9
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Default Re: Bush BTV183DVD/A frame collapse

When I first saw the heading I thought it was one of my favourite old black and white TVs, the Bush TV183D!
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Old 23rd Jun 2021, 6:10 pm   #10
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Default Re: Bush BTV183DVD/A frame collapse

Mick very kindly sent me a new frame chip, but the results are the same, I even reflowed the frame section, just in case.

I still think it could be capacitor related, as I get a full raster when first switched on after being unplugged for a day, then it jumps down to about 2", then total collapse.


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Old 23rd Jun 2021, 6:37 pm   #11
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Default Re: Bush BTV183DVD/A frame collapse

seem to remember having frame problems that was down to poor connections on the scan coil plug and socket ,even hard wired some .
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Old 23rd Jun 2021, 6:44 pm   #12
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Default Re: Bush BTV183DVD/A frame collapse

Does the frame chip have a supply or is there an o/c safety res failed ?
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Old 24th Jun 2021, 6:22 am   #13
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Default Re: Bush BTV183DVD/A frame collapse

I have checked the connections to the scan coils, no problems found.
I will change out the remaining small electrolytics & check all resistors.
I have reflowed the entire frame section, so can rule out any dry joints.


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Old 24th Jun 2021, 7:00 am   #14
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Default Re: Bush BTV183DVD/A frame collapse

Is there voltage on the frame chip?
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Old 24th Jun 2021, 9:05 am   #15
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Default Re: Bush BTV183DVD/A frame collapse

I'd do as suggested and hang a meter on the feed pin(s) of the chip. If they remain steady or rise slightly when the fault is there then I'd turn my attention to the frame generator stage.As I said earlier, I seem to remember an awkward fault like this on an Orion chassis was due to a small (non-electrolytic) in this stage. You might need the diagram.
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Old 24th Jun 2021, 9:16 am   #16
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Default Re: Bush BTV183DVD/A frame collapse

Might be worth checking that the 'sync chip' has got it's supply, often 12v from the mains psu. Also check all the rectifier diodes in the psu secondary for dry joints as well as checking output voltages from them. It's not uncommon for a diode to go short or leaky, which then removes a supply voltage.

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Old 24th Jun 2021, 12:48 pm   #17
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Default Re: Bush BTV183DVD/A frame collapse

Keep looking for the obvious first with the various suggestions from others.... Voltage remaining on the frame IC, sync pulse etc.

However - I do seem to remember a batch of this chassis which suffered from the scan coils failing as they warmed up.
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