UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Closed Thread
 
Thread Tools
Old 22nd Apr 2019, 6:57 pm   #21
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

That's a very nice list and gives me quite a few ideas, thank you very much!
Retrorepair is offline  
Old 22nd Apr 2019, 8:29 pm   #22
Michael Maurice
Moderator
 
Michael Maurice's Avatar
 
Join Date: Feb 2006
Location: Wembley, Middlesex
Posts: 7,219
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

What happens if you disconnect the line output stage?

I'm wondering if the LOPT is faulty.
__________________
Forum Moderator

http://www.michaelmauricerepairs.co.uk/
Michael Maurice is online now  
Old 23rd Apr 2019, 6:58 am   #23
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

Yeah I'm starting to wonder the same thing. I replaced it with a brand new HR 7244 which is what was recommended but maybe it was a duff. Occasionally it will turn on as in I can hear sound but no tube activity which is what the fault was before except the tube would fire up. The other chassis I've been borrowing parts from has a good LOPT but it's a 21" tube so wasn't sure if it would work on a 29". Looks identical but as I don't have a service manual for this other one I wasn't sure if I should try it.
Retrorepair is offline  
Old 23rd Apr 2019, 8:26 am   #24
HamishBoxer
Dekatron
 
HamishBoxer's Avatar
 
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,923
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

Is there a number on the loptx,s?
__________________
G8JET BVWS Archivist and Member V.M.A.R.S
HamishBoxer is offline  
Old 23rd Apr 2019, 8:44 am   #25
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

I couldn't see any but will check later. It has just dawned on me that I've been using the 25" service manual as my reference as I couldn't find the 29. Could be it's under powered but I'd expect some life in the tube?
Retrorepair is offline  
Old 23rd Apr 2019, 9:36 am   #26
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

Well the list8ng indicates it should be fine for a 21 up to 29" tube so might just be a duff.
Retrorepair is offline  
Old 23rd Apr 2019, 9:42 am   #27
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

I don't think the 21" and 29" tubes have the same scanning angle. There will be considerable differences timebase wise at least. J.
Heatercathodeshort is offline  
Old 23rd Apr 2019, 9:44 am   #28
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

This is the listing: https://rover.ebay.com/rover/0/0/0?m...2F273107970600

I can't find reference anywhere else to HR 7244 except donburg which says it's for a 21".
Retrorepair is offline  
Old 23rd Apr 2019, 10:05 am   #29
Maarten
Dekatron
 
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,185
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

What's the number on the original transformer? It should look something like 1-439-xxx-xx or maybe other numbersin the same format.

That's really the most reliable way to find a replacement. Mind you, it's not 100% certain that it's broke but at least it will be good to know whether the replacement should be expected to work or not.

Also, could you confirm the model number of the TV set? There might be a letter missing.

Last edited by Maarten; 23rd Apr 2019 at 10:19 am.
Maarten is offline  
Old 23rd Apr 2019, 10:33 am   #30
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

It's definitely KV-E2912U though the closest document I've found is here: https://www.electronica-pt.com/esque...ileinfo/34350/

A quick google search confirms it does indeed have a 1-439-416-11 which a quick google search indicates HR-7244 should replace.
Retrorepair is offline  
Old 23rd Apr 2019, 11:38 am   #31
Maarten
Dekatron
 
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,185
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

I missed the letter E, so now the model number is clear and can be used to look up the transformer.

Googling something that is in front of you might not be the most accurate way to determine a part number as opposed to looking at the actual part.

I checked with Aswo and they mention 1-439-416-11, -12 as originals and -51 and -52 as original replacements. Strangely, Efiter (the transformer manufacturer) gives HR7244, HR7244, HR7243 and HR7245 as replacements for those four, respectively.

I think it's safe to conclude that a HR7244 should be fine in this set.

Now to determine whether it and the original are indeed defective, or that there's some other fault in the set (FBT's were always blamed, it's a tradition of sorts). Maybe use a ring test? Did you test the power supply loaded with a light bulb instead of the line output stage? You say the tube
'fired up' before, do you mean you saw the heater light up? In that case the FBT was probably fine. Maybe the G2 voltage was low or missing or the vertical deflection. If the heater doesn't light up anymore, there may now be additional faults.

Last edited by Maarten; 23rd Apr 2019 at 11:55 am.
Maarten is offline  
Old 24th Apr 2019, 11:51 am   #32
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

I'm sure there's additional faults as I don't seem to be getting 27v tested directly from the FBT.

I'm going to see what happens when I put the original FBT in.

What I am getting is (while the TV thinks it's on):

27v = 0
12v = 6.5v
5v = 2 8v
G2 = 52.4v
H1 = 117.8v
H2 = 118.1v
Blue gun = 120.1v
Green gun = 120v
Red gun = 116v
Retrorepair is offline  
Old 24th Apr 2019, 6:08 pm   #33
Maarten
Dekatron
 
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,185
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

The 27V line seems suspicious. Have you tested for shorts there? I haven't looked up the schematic yet, but isn't it used for vertical deflection?

When you say "directly from the FBT", do you mean after the respective rectifiers, or right at the physical connections of the FBT itself?
Maarten is offline  
Old 24th Apr 2019, 8:14 pm   #34
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

There's no 27v (well 0.02v) right at the FBT itself, let alone the VM board. Yes it is used in deflection. I was a bit concerned to see it was a dead short with ground but on my working chassis (21" AE1-C) it's the same.

Just wondering if it only outputs 27v if HV is running (which I assume it isn't)?

That's the old and the new FBT that give exactly the same result so would be inclined to say it's not that.
Retrorepair is offline  
Old 24th Apr 2019, 9:05 pm   #35
Red to black
Nonode
 
Red to black's Avatar
 
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
Posts: 2,473
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

Re:27V supply, You will get a low ohms reading to chassis there (at the FBT pin) as the other end of that winding inside the transformer is connected to chassis (via pin 11 FBT), have a look at the circuit diagram.

Another thing is you will not get any (sensible) DC reading at that point either, even if the line stage was running correctly as it is primarily a pulsed (at line rate) voltage, you need to measure the DC voltage at the associated rectifier output/smoothing capacitor (C801 +), and also as it is a lopt derived supply the line output section would need to be running correctly for this to be present.

On this chassis, as it now aged and with this type of fault I would start by replacing all 4 of the Electrolytic capacitors in the primary side of the PSU, also the smoothing capacitor (another Electrolytic) for the 14 V rail on the secondary side of the PSU this time (C615), was known for giving problems years ago too.
In case you are not aware Electrolytic capacitors are polarised, ie. have to be fitted the correct way round.
__________________
I don't suffer from Insanity. I enjoy every minute of it.

Last edited by Red to black; 24th Apr 2019 at 9:17 pm. Reason: adittional info, component refs
Red to black is offline  
Old 25th Apr 2019, 12:29 am   #36
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

Excellent, so I can rule out 27v as an issue in this state.

I have already changed all the electrolitics in the primary/secondary sections. Yes I'm fully aware how age and heat can affect them, polarity also but thanks for the warning anyway. Best to say it just in case.

This is going to turn out to be something silly I'm betting by this point. Ive changed out most of the usual suspects if not all.
Retrorepair is offline  
Old 25th Apr 2019, 3:40 am   #37
Maarten
Dekatron
 
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,185
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

You can't rule it out at this point, since the only way to take measurements is after the respective rectifier. This goes for all FBT derived DC voltages.
Maarten is offline  
Old 25th Apr 2019, 10:14 am   #38
FrankB
Heptode
 
Join Date: Oct 2005
Location: Olympia, Washington, USA.
Posts: 663
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

You might check the .1 mfd or 1 mfd cap feeding the H driver tx and re-solder the pins on it too.
I found many of them bad, and they can cause the HOT xistor to fail.
Please remember that on Sony, any semis should be OEM. Their sets do not respond well to universal semis. The specs on their xistors are critical to proper operation of the set.
Been there & have the hat on that one. HTH
FrankB is offline  
Old 25th Apr 2019, 10:43 am   #39
Retrorepair
Pentode
 
Join Date: Apr 2019
Location: Denbigh, Wales
Posts: 149
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

I thought 27v would only be generated if HT is running?

I've now changed all electrolytics (not touched the audio section though).

The list of parts changed has grown somewhat, and STILL no change at all:

Q609
D601
C818
IC502
T802
C604
IC601
D612
D910
C613
PS601 + PS602 tested ok
D801
C811 (2.2uf instead of 2.0uf)
Q805
C825
T801
R809
Q604 (swapped for Q507, canal +blk)
T602
C804
R807
D803
C605
C617
C611
C608
R831
IC501 (TEA2028B)
IC604 (5v reg)

Really don't want to scrap this one, it's taken me literally years to find a 29" AE-1A set and they're only getting harder to find.

Thank you all for the help so far, hopefully it will yeild some results soon!
Retrorepair is offline  
Old 25th Apr 2019, 11:08 am   #40
Maarten
Dekatron
 
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,185
Default Re: Sony KV-2912U - won't turn on - AE-1A chassis

Changing huge amounts of random parts seldomly works and opens up the chance of introducing new faults. I think if you want to do this repair yourself, you won't be able to fullly take advantage of troubleshooting tips an hints until we've established what you know about troubleshooting and underlying theory of electronics and what you need to know more before proceeding.

The general direction of the troubleshooting needs to be more measuring, less replacing. Two kinds of measurements are particularly useful starting out in situations like this. Measuring DC voltage (after the diode, not on the transformer pins) and measuring for shorts downstream (using diode mode on the meter).

Last edited by Maarten; 25th Apr 2019 at 11:17 am.
Maarten is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:23 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.