Sony Trinitron KV-1921

[Findm-Keepm]

Here's some tips for your set - the KV1920/KV1921 are similar sets - notice how most cures are by replacing a cap? Caps fail from use - most have a shelf life of 2X-3X the service life. Heat + ripple current are the two most common external failure sources...

[Jon A.]

Super, thanks. Funny, I always thought electrolytics went bad faster if unused.

[Findm-Keepm]

Originally Posted by Jon A.

Super, thanks. Funny, I always thought electrolytics went bad faster if unused.

A common misconception - folks see the "shelf life" rating on a data sheet, note that it is shorter than the "endurance" (service) rating, and make the assumption. Hint: the shelf life is specified for storage at either 85 or 105 degrees Celcius, not room temperature (25 degrees C). NOBODY stores caps at either temp (185 degrees and 215 degrees Fahrenheit!!). The US DoD specifies storage at less than 35 degrees Celcius (95 degrees F) - big difference, and shelf life is magnitudes greater at the lower temps, as would be expected.

Over on DIYAudio, the threads are hilarious with the folks that can't/won't read a datasheet for capacitors or transistors. Most just don't want to admit they didn't know what they were looking at.

One thing I was always thankful for was an explanation of all the transistor parameters before learning the applications... Hie, Hfe, Hoe, VCeo, VCbo and others - all important, especially on the mid-terms exams.

I learned most of my theory through various schools and bench experience in the 80s, but in 1995, I bought a copy of "The Art of Electronics" - best all-in-one theory and application text I've found. Not light reading, but a good way to have some "A-ha!" moments when things are explained clearly. Cool fact: I sold a service manual for a Transistor Analyzer to one of the authors (Horowitz) back in 2010.

I found the gouge for checking the SG-608 and SG-613's with an ohmmeter - they are in a couple of Sony Bulletins. I'll scan them this weekend when I get a chance. I may also make up a matrix that lists early Sony color sets by model and what HOT they use - the SCSs (SG-613, SG-608s) or transistors (2SC1316/2SC1034, etc.). That would go a long way for folks looking at potential Sony sets to save. Me, no problem with the SG-613 sets - I used to own two, and have some spares, except for the 2SC1034s. The best spares for Sonys are still some 4.7uF 250V caps.....and solder (for the later 80s sets with the bad IF solder connections).

Cheers,

[Jon A.]

I don't think I have seen any capacitor datasheets. I may have picked up that misconception from various posts here. I should try to get a bulk lot of capacitors then; ordering them individually would be a royal pain.

That book sounds pretty good to me. The way learn means I wouldn't read it cover to cover, but it would be great for occasional reference.

I'm not too concerned about what HOT the Sony sets use, not anymore. A big plus to me is that they made a lot of table sets, and I need another console like I need a hole in the head. I'll still take consoles if I like them enough though.

[ChrisW6ATV]

Originally Posted by Findm-Keepm

Here's some tips for your set - the KV1920/KV1921 are similar sets - notice how most cures are by replacing a cap? Caps fail from use - most have a shelf life of 2X-3X the service life. Heat + ripple current are the two most common external failure sources...

Thank you for posting that list, Brian. I worked on commercial Sony color monitors for 20+ years until recently and kept a comparable list for them, but I never did much with consumer sets.

[Alastair E]

Ah--The Sony GTO Line-timebase silicon switch 'Orrible bloody things!!.....

In UK, we had rather an infamous Sony model, the KV1810UB and KV1810 MkII.--Actually quite a compact neat set with great performance if the CRT was good

Both these sets used a SG-613 GTO in both the PSU stage and the horiz out. A Dry-Joint or failure of 19V rail would kill the horiz out GTO--the short then on the +B line would kill the PSU one...

These SG-613 were around £15 Each here, and a normal horiz-out transistor like a BU208 or BU508A maybe £1-2 at the time, so £30 in parts before you even started on one of these 1810's, Plus the so-called, 'Kit' of other crap you needed to change according to Sony, as a reliability measure--That didn't cure the blowing SG issues....

Wasn't long before a bright spark came up with a way to use a standard Horiz O/P Bipolar Transistor in place of both the PSU and Horiz-Out GTO's....

Involved changing the Drive Transformer for a type used with Horiz-Output Transistor, and deleting the original GTO drive circuit.
A BU508A was used quite successfully to sub the SG GTO with the alterations to drive it right by replacing the drive transformer by me for a number of these repairs, and was a good reliable conversion.
On a few of the earlier conversions, I retained the SG in the PSU (as I had sill a few around) and just modded the horiz-out stage. I kept one of those early ones for may years and no further trouble from it.

[Jon A.]

Originally Posted by Alastair E

Wasn't long before a bright spark came up with a way to use a standard Horiz O/P Bipolar Transistor in place of both the PSU and Horiz-Out GTO's....

Involved changing the Drive Transformer for a type used with Horiz-Output Transistor, and deleting the original GTO drive circuit.
A BU508A was used quite successfully to sub the SG GTO with the alterations to drive it right by replacing the drive transformer by me for a number of these repairs, and was a good reliable conversion.
On a few of the earlier conversions, I retained the SG in the PSU (as I had sill a few around) and just modded the horiz-out stage. I kept one of those early ones for may years and no further trouble from it.

That must be the mod I heard a passing mention of. Where can I find instructions on how to do that?

[Findm-Keepm]

Originally Posted by Alastair E

Ah--The Sony GTO Line-timebase silicon switch 'Orrible bloody things!!.....

In UK, we had rather an infamous Sony model, the KV1810UB and KV1810 MkII.--Actually quite a compact neat set with great performance if the CRT was good

Both these sets used a SG-613 GTO in both the PSU stage and the horiz out. A Dry-Joint or failure of 19V rail would kill the horiz out GTO--the short then on the +B line would kill the PSU one...

These SG-613 were around £15 Each here, and a normal horiz-out transistor like a BU208 or BU508A maybe £1-2 at the time, so £30 in parts before you even started on one of these 1810's, Plus the so-called, 'Kit' of other crap you needed to change according to Sony, as a reliability measure--That didn't cure the blowing SG issues....

Wasn't long before a bright spark came up with a way to use a standard Horiz O/P Bipolar Transistor in place of both the PSU and Horiz-Out GTO's....

Involved changing the Drive Transformer for a type used with Horiz-Output Transistor, and deleting the original GTO drive circuit.
A BU508A was used quite successfully to sub the SG GTO with the alterations to drive it right by replacing the drive transformer by me for a number of these repairs, and was a good reliable conversion.
On a few of the earlier conversions, I retained the SG in the PSU (as I had sill a few around) and just modded the horiz-out stage. I kept one of those early ones for may years and no further trouble from it.

Got a schematic of the mod, or a pix of a modd'ed set? Or a copy of the magazine article? That would be something, to get these old Sony sets going again on transistors instead of GCS'.

[Findm-Keepm]

Originally Posted by jon a.

edit: I found some info on the uk vintage radio site. Who knows if such a mod will work for other sony sets, but it's worth a look.

url?

[Jon A.]

...

[Findm-Keepm]

Those modify the set to keep from blowing the SG608/SG613 - they don't show how to modify the set to use a bipolar transistor output.

Apparently, the February 1987 issue (page 252) of Television magazine (a UK publication aimed at TV repair engineers) has the modification. I found a 2007 posting referring to the article, but no article. I have several issues, bought when I was in England in 1987/1988, but my earliest is October 1987. I bought them as a novelty - each issue had a freebie taped to the cover, from wire ties to a resistor color code decoder, and one even had a silicon diode assortment, all BAT-series stuff.

[Alastair E]

It Really IS an easy mod....

Choose a Horiz Drive Tx from any popular set that uses a conventional Transistor.

Remove the Original Sony Tx and replace.

Only issue--The Sony uses the 19V rail (In the case of the 1810) to supply the drive stage. You'll Maybe have to alter the drive transistor and or the supply to it--To match that of the donor transformer, so if the Donor set uses a full (say 120V +B) to the drive Tx, then you'll need to supply the modded stage with that voltage, and change the drive transistor.

The Base circuit for the Horiz Out should also match that of the donor set.

[Jon A.]

Originally Posted by Alastair E

The Base circuit for the Horiz Out should also match that of the donor set.

Are you referring to the voltage going to the transistor's base leg?

[Findm-Keepm]

Originally Posted by Alastair E

It Really IS an easy mod....

Choose a Horiz Drive Tx from any popular set that uses a conventional Transistor.

Remove the Original Sony Tx and replace.

Only issue--The Sony uses the 19V rail (In the case of the 1810) to supply the drive stage. You'll Maybe have to alter the drive transistor and or the supply to it--To match that of the donor transformer, so if the Donor set uses a full (say 120V +B) to the drive Tx, then you'll need to supply the modded stage with that voltage, and change the drive transistor.

The Base circuit for the Horiz Out should also match that of the donor set.

Base to gate, Cathode to emitter, and Anode to Collector? Swap out driver transformer with one from a transistor set? Change the drive transistor to what? I've seen low and medium power horizontal drive transistors. Any problems with ringing or drive lines from the changed impedance of the output transistor?

Much more is needed - and I'm coming at this with over 30 years experience...

Sony used different gating methods in the SG608/SG613 sets, with some of the drive coming from another SCS, like the SG629. One size fits all isn't going to work in all sets - and the mod in the UK magazine was for the KV-1800UB, a set without a direct US analog.

Not a skeptic, just more detail is needed - not everyone here is overly familiar with the Sony circuit, much less one without a schematic....

[Findm-Keepm]

Originally Posted by Alastair E

It Really IS an easy mod....

Choose a Horiz Drive Tx from any popular set that uses a conventional Transistor.

Remove the Original Sony Tx and replace.

Only issue--The Sony uses the 19V rail (In the case of the 1810) to supply the drive stage. You'll Maybe have to alter the drive transistor and or the supply to it--To match that of the donor transformer, so if the Donor set uses a full (say 120V +B) to the drive Tx, then you'll need to supply the modded stage with that voltage, and change the drive transistor.

The Base circuit for the Horiz Out should also match that of the donor set.

Base to gate, Cathode to emitter, and Anode to Collector? Swap out driver transformer with one from a transistor set? Change the drive transistor to what? I've seen low and medium power horizontal drive transistors. Any problems with ringing or drive lines from the changed impedance of the output transistor?

Much more is needed - and I'm coming at this with over 30 years experience...

Sony used different gating methods in the SG608/SG613 sets, with some of the drive coming from another SCS, like the SG629. One size fits all isn't going to work in all sets - and the mod in the UK magazine was for the KV-1810UB, a set without a direct US analog, but probably close to the KV-1710, the FTC mandated 17" vs almost-18" screen.

Not a skeptic, just more detail is needed - not everyone here is overly familiar with the Sony circuit, much less one without a schematic....