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1971 Beovision 3200
1971 Bush CTV1120
Granada Television Brochure, 1970s
Long Gone UK TV Shops
Memories of a Derwent Field Service Engineer
PYE Australia Circa 1971
Radios-TV VRAT
Fabulous Fablon
Thorn TX10 Chassis
Crusty-TV Museum, Analogue TV Network
Philips N1500 Warning!
Rumbelows
Thorn EMI Advertising
Thorn’s Guide to Servicing a VCR
Ferguson 3V24 De-Robed
Want to tell us a story?
Video Circuits V15 – Tripler Tester
Thorn Chassis Guide
Remove Teletext Lines & VCR Problems
Ceefax (Teletext)
Suggestions
Website Refresh
Colour TV Brochures
1970s Lounge Recreation
CrustyTV Vintage Television Museum
Linda Lovelace Experience
Humbars on a Sony KV2702
1972 Ultra 6713
D|E|R Service “The Best”
The one that got away
Technical information
The Line Output Stage
The map
Tales of a newly qualified young engineer.
Tales of a Radio Rentals Van Boy
Sanyo SMD
Disastrous Company Rebranding
1969 Philips G22K511
Memories Of The TV Trade
Crazy house
Dirty TV screens
Dual Standard and Single Standard CTV’s
Radios-TV on YouTube
The Winter of 62/63
A domestic audio installation
1979 Ferguson Videostar Deluxe 3V16
Music centre modifications
Unusual record player modification
B&K 467 Adapters
Mishaps In The Trade
1971 Beovision 3200
1971 Bush CTV1120
Philips G17T320
I originally bought this set for its looks and recently have been working on it having left it in store for several years.
It came with a fault. It didn't work and smoke was coming from a small component next to a replacement capacitor.
Having sorted the basic power supply section I moved on to the smoker which was a high voltage diode producing boosted ht(tp20) from a winding on the LOPT. The cap had presumably failed and taken the diode with it. Having replaced the diode (2469) I was rewarded with a picture with reduced width. I checked the boost voltage to find it was 1050volts on a 1kv cap (2468) and the voltage on the focus anode was very high. (no wonder the original cap failed). I had already replaced the tuning cap across the line o/p transistor,(2461) as the original had lost most of its capacity. Now I assumed this would have caused the over-voltage in the set's previous life but it still had the same problem. I've checked all components in this area including the drive from the line oscillator i/c (point 30) and can find nothing out of spec. The line signal @point 30 is 9.5 volts and is correct. The signal @ point 31 should be 180 volts but is way over 200. I cannot fault any components and the DC conditions are right. I assume this is why the boost voltage is way too high. The line drive transistor (2404, BF337) checks out but is showing a gain of 80 when all the listings I can find are talking about a minimum of 20 with no upper limit listed. In the meantime I have added 500pF across the tuning cap to bring the boost ht down to a safer level and have increased the value of R2414 to 2.2k which has lowered the ht even more.
Can anyone advise me about TWO things.
Is this high ht a symptom of too much gain in the BF337 line drive transistor and given this work so far there has been absolutly no change in the width problem. I have ring-tested the LOPT and I believe it to be fine. The LOP transistor (4460 BU105) checks out with two diode drops and a gain of 4. The only clue might be that the raster is very cramped on the left edge (possibly with a fold)
with little or no actual linearity problems over the rest of the scan. Nothing seems to affect this so far. I'm hoping this problem is recognised and I'm hoping for a bit of help as I've run out of ideas atm.
Hi Jonathan,
Lovely sets these, I've often been tempted to get one, they look especially nice on their chrome pedestal stand.
Have a look in the data library, you find an excellent article by LLJ covering this chassis. Its also recommended you change the BU105 for a BU205.
Anyway have a look in the data library under "Service Dept"| " Service Data Library", then.
- Les Lawry-Johns
- -----LLJ 1976-1977
- ----------The file is LLJ No 244 Philips 320 Chassis
CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek
Check to see if any work has been carried out around the line driver chip (I think it's a TBA720 A or AQ). It's years since I saw one of these and when I was at Philips I know some changes were made in this area. From memory (which is not what it was) the chip was changed from a TBA720A to an AQ (possibly BQ) type. They are not directly interchangeable and some changes were made to accommodate the new chip. The data library may cover this with the article mentioned above. I mention this because if the mods weren't done, there may well be a drive problem. I can't remember now what happened if the chip was changed without the mods being done.
With the HT being high does that point to a fault in the PSU, or is the HT tied in with the line stage in some way?
I don’t have a circuit at the moment, I will try and look at the articles posted by Chris later.
Frank
I can remember seeing one or two of these set's whilst at the co-op in the late 80's. They were normally a nicotine yellow ! This one is nice and white and looks a corker. Very stylish 🙂
To understand the black art of electronics is to understand witchcraft. Andrew.
CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek
The LLJ article does document the TBA720 IC, worth a read, the conduction of the driver transistor is quite critical and is adjusted by “select on test” of R2409 with one of the versions of the IC.
Frank
There's upstairs above the shop. Given time to recover and then I'll have go at it.
The wood cabinet models 322 and 324 must be quite rare. Didn't have many out on rental, customers liked the super slim teak cabinet. But by 1973 demand for black and white TVs was in decline.
Till Eulenspiegel.
Isn’t it past your bed time in the ward, be getting to trouble with the nurses. 🙂
Frank
Posted by: NuvistorIsn’t it past your bed time in the ward, be getting to trouble with the nurses. 🙂
Or is that the plan David 😉
Marc
BVWS member
RSGB call sign 2E0VTN
Let's hope it's not the other way around ....... erm, ahem.
To understand the black art of electronics is to understand witchcraft. Andrew.
Hi Jonathan,
I'm stunned just how 'white' the cabinet appears to be, all the ones I've seen have all gone cream. Nice set.
Marc
BVWS member
RSGB call sign 2E0VTN
Posted by: MarcHi Jonathan,
I'm stunned just how 'white' the cabinet appears to be, all the ones I've seen have all gone cream. Nice set.
Perhaps it was kept out of direct sunlight, or has had the peroxide treatment?
Then again some plastics were more resistant to fading than other. I own a 1983 Teleton which is still pristine white and also a Braun hairdryer where parts of the case have yellowed whereas other parts have remained white.
Thank you all for your replies. The cabinet has been 't-cut' and looks well if still a little yellow. If or when I have it working properly I'll strip and spray the pedestal which has oxide breaking through the paint. I wonder if anyone has advice on the scan problem. I think I have forgotten what causes left cramping and folding. Can anyone remind me please.
Posted by: ChrisHi Jonathan,
Lovely sets these, I've often been tempted to get one, they look especially nice on their chrome pedestal stand.
Have a look in the data library, you find an excellent article by LLJ covering this chassis. Its also recommended you change the BU105 for a BU205.
Anyway have a look in the data library under "Service Dept"| " Service Data Library", then.
- Les Lawry-Johns
- -----LLJ 1976-1977
- ----------The file is LLJ No 244 Philips 320 Chassis
Thank you Chris. I believe I have not yet qualified for access to the libary.
Hi Jonathan,
if you had tried you would have found you had an early Christmas prezzy and do have access. 🙂
If did try but found you were blocked, try logging in and out and if that still fails clear cache and cookies
Chris
CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek
Have a look at the on time of the driver transistor, as per the LLJ article. I am not sure from your first post if it is HT that is high or just the Boost volts.
I have not worked on these sets, so advice from me is going to be sparse.
Frank
I think the main HT on these is 160V, the boost I can't remember but probably around 600-700V
Posted by: ChrisHi Jonathan,
if you had tried you would have found you had an early Christmas prezzy and do have access. 🙂
If did try but found you were blocked, try logging in and out and if that still fails clear cache and cookies
Chris
Wow Chris thank you very much.
Posted by: sidebandCheck to see if any work has been carried out around the line driver chip (I think it's a TBA720 A or AQ). It's years since I saw one of these and when I was at Philips I know some changes were made in this area. From memory (which is not what it was) the chip was changed from a TBA720A to an AQ (possibly BQ) type. They are not directly interchangeable and some changes were made to accommodate the new chip. The data library may cover this with the article mentioned above. I mention this because if the mods weren't done, there may well be a drive problem. I can't remember now what happened if the chip was changed without the mods being done.
Thanks for the suggestion but it's the original 720 Not the 720AQ.
I've done some work to correct the dc conditions but this had no effect on my two problems and the signal voltage and duty cycle are correct at the output.
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