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-   -   Is it a Bush TUG.68 ? (https://www.vintage-radio.net/forum/showthread.php?t=105321)

Stubble 13th May 2014 9:48 am

Re: Is it a Bush TUG.68 ?
 
Hi John

Tested as you describe and nothing, I will have some more time on the weekend, my order of capís and resistors has arrived so all systems go.

Cheers Lee
:wave:

Stubble 17th May 2014 1:27 pm

Re: Is it a Bush TUG.68 ?
 
4 Attachment(s)
Afternoon chaps :wave:

Right changed capís C16 and C26 so that all the caps under the tag board done. :wall:

Powered up and still no raster. :angry:

Mike (ekcopyephilips) sent me in the post the replacement LOPT, many thanks Mike. :thumbsup:

The new LOPT spent a few nights in the central heating duct getting nice and warm and driving out any dampness.

I fitted the new LOPT this morning and we have first light, now I need to work on the frame out put. :clap:

Photos of the replacement LOPT and the raster achieved.

John (Heatercathodeshort) if you like I could send the original LOPT for you to have a look at and see if you can find the break in the EHT winding?
PM me your address if you like.

Lee

mark pirate 17th May 2014 1:58 pm

Re: Is it a Bush TUG.68 ?
 
Good progress so far, I would check the windings of the blocking tx, this could be causing the frame collapse if you have already replaced the caps in the frame stage.
:beer:
Mark

Stubble 17th May 2014 4:19 pm

Re: Is it a Bush TUG.68 ?
 
2 Attachment(s)
Frame output re-capped

Stubble 17th May 2014 5:46 pm

Re: Is it a Bush TUG.68 ?
 
3 Attachment(s)
Waxies changed in the receiver, now the frame is locked but the raster is doubled what would be causing this?

Resistors to check next.

Lee

Heatercathodeshort 18th May 2014 1:33 pm

Re: Is it a Bush TUG.68 ?
 
You have a PM Lee.

Heatercathodeshort 18th May 2014 7:22 pm

Re: Is it a Bush TUG.68 ?
 
The line oscillator is running well off frequency. Replace all the wax caps, check resistor values and replace any that are more than 20% out. [In line osc circuit] Test line discriminator diodes as one may be O/C. Line hold should lock about mid way. J.

Stubble 20th May 2014 9:35 pm

Re: Is it a Bush TUG.68 ?
 
2 Attachment(s)
Evening some more progress. ;D

As advised by John I duly checked the resistors in the line oscillator.

Four where out of tolerance and changed.
R31, 32, 39 and the one that made the greatest improvement R35 :thumbsup:

The raster is getting there, out of focus, which I will tackle later; the adjustment leaver is stuck and can be sorted when I strip the cabinet down for refinishing. The implosions glass and the face plate of the tube are thick with dirt which doesnít help..

Frame oscillator and output next.

Focus Diode 20th May 2014 9:46 pm

Re: Is it a Bush TUG.68 ?
 
Great progress there. Well done! Won't be long before you'll have a correctly adjusted picture.

Cheers,
Brian

mark pirate 20th May 2014 10:17 pm

Re: Is it a Bush TUG.68 ?
 
You are getting close now:clap:
You just need to sort out the linearity and centre the picture, the focus units always seem to seize up with years of disuse. Remove it from the tube before attempting to free it up!
:beer:
Mark

Heatercathodeshort 27th May 2014 9:45 pm

Re: Is it a Bush TUG.68 ?
 
5 Attachment(s)
Quote:

Originally Posted by Stubble (Post 681846)
John (Heatercathodeshort) if you like I could send the original LOPT for you to have a look at and see if you can find the break in the EHT winding?

The LOPT arrived this morning and as Lee discovered, the EHT overwind was O/C. This is very unusual with this transformer as they are one of the most reliable flyback transformers ever produced.
Examination under a powerful magnifier came up with nothing so it was decided to attempt to locate the finish [EY86 end] of the overwind.
A hot air gun was used to soften the pitch coating and a little prodding with a needle revealed the cloth tape covering the take off lead to the rectifier. This was heated with care and the cloth tape picked away taking precautions to prevent damage to the very thin wire employed. After a while it was possible to locate the end of the winding and with tweezers unwide a few turns. Luck was on my side and after just four turns the break was discovered caused by 'Green Spot'. After once again locating the 'new' end I removed a few turns to check the wire was in good condition then removed any lose pitch to reveal a clean winding.
A new lead out wire was soldered to the fine wire and secured with tape to the overwind. Finally a layer of insulating epoxy resin was made up and applied to the entire overwind.
The transformer was then fitted into a really scruffy, smoke ridden TV63 that has been under the bench for years. It looks as if it's spent most of it's life keeping a night watchman [do you remember them?] company in an unsavory part of Newcastle.. He probably had it plugged into a street lamp. [Oh I forgot David you were still on gas lighting back then] It has been working fine for a good few hours, so let us hope it continues to do so.
Just a challenge, a bit of fun and nothing to lose! Pics show the fine wire just before fitting the new lead out, progress and the final test. Regards, John.

FERNSEH 27th May 2014 10:17 pm

Re: Is it a Bush TUG.68 ?
 
Nice neat repair John. Now I did see a lot of these Bush TVs in the 60s. The Bakelite cabinet TV62 was popular here in the North-East.
As you say the line output transformers were reliable, a very simple design. The primary winding is connected between the anode of the PL81 and cathode of the boost diode PY81, an EHT "tyre" and a few turns for the EY86 heater. EY51 in early production models, TV53/63. A clever line output stage which used high impedance scan coils. Peto-Scott employed something similar.

DFWB.

mark pirate 28th May 2014 8:33 am

Re: Is it a Bush TUG.68 ?
 
Nice work John, It was only years of damp storage that damaged it, Bush LOPT's from this era never fail, but as we know the Bush LOPT's from the 60's were a different story!
:beer:
Mark

Stubble 28th May 2014 7:07 pm

Re: Is it a Bush TUG.68 ?
 
Great job John, if I had tryed it would have ended badly for the LOPT for sure.

Away from home at the moment so no progress but back next week and back to the old bush :-)

Heatercathodeshort 28th May 2014 7:35 pm

Re: Is it a Bush TUG.68 ?
 
I'll post it back in the next few days Lee. John.

Stubble 5th Jun 2014 8:09 pm

Re: Is it a Bush TUG.68 ?
 
Hi John the LOPT arrived today; wow you have done a great job too, thanks very much. ;D

I have been away for the last week so nothing doing, itís back to this setís restoration on the weekend time allowing, Iím going to change a few out of tolerance resistors in the sync and frame stages next. :)

I will also reinstall the original LOPT and see how it works out.

Lee :thumbsup:

Heatercathodeshort 5th Jun 2014 8:46 pm

Re: Is it a Bush TUG.68 ?
 
I hope it holds up Lee. It was more of a 'I wonder why it's gone O/C' than a professional repair. Time or lack of it will tell! Cheers, John.

Stubble 7th Jun 2014 3:48 pm

Re: Is it a Bush TUG.68 ?
 
5 Attachment(s)
Up-date

Replacement of the remaining out of tolerance resistors completed.
Replacement of all wax caps completed.

Removed focus unit and cleaned and released the adjustment control with WD40
Gently cleaned dust off scan coils and replaced focus unit.

On powering up adjustment of the ion trap was required to achieve the brightest raster possible and adjustment of the centring control and where there.

The raster is not completely rock steady itís a bit jumpy every now and then and Iím assuming this is down to the electrolytic caps, which I will now look at.

Niggling faults:

The sound pot is very scratchy and the sound drops off till you readjust it.
Brightness pot is also scratchy at times.
Clean the face plate of the CRT and the inside face of the implosion screen.

Run the set for about 2 hours and no other problems materialized so far.


Lee

Stubble 26th Jul 2014 1:40 pm

Re: Is it a Bush TUG.68 ?
 
3 Attachment(s)
Ho do everyone

Been a while since I updated on this set.

The main smoothing cap decided to give in and surrender itself to its maker, bang and the cap has gone.

I tried re-stuffing the original can but it being quite a slim unit I just couldnít cram the new ones in, being ham fisted I crushed the empty can and made a complete mess of it.

To resolve this little problem for now I fitted a new can which is a little bigger and wonít fit into the cut out in the chasses so I secured it to the side of the chasses and temporary tacked the wires onto the original connections so if I do find a slimmer caned unit it can be swapped out.

Stubble 26th Jul 2014 1:59 pm

Re: Is it a Bush TUG.68 ?
 
3 Attachment(s)
I then turned my attentions to the cabinet.

First removing the doors and repairing the right have one which had slit where the pivot hinge bored down into the door, this was glued and clamped over night.

Next all the hardware was removed and a chemical assault took place, first the original finish was removed and then wood worm treatment although it seems historical activity (small patch of flight holes in the left hand side and one or two in the back sub frame) this treatment being repeated three times covering the entire cabinet to excess and then left to dry out. I removed the foil paper shielding from inside the cabinet so that all inside surfaces had good coverage, the foil was in bad shape and pretty much most of it had rotted away from being damp for a long time.

About six hours of sanding filling and more sanding wire wooling followed.
I pasted tin foil inside the cabinet with wall paper boarder adhesive to reinstate the shielding time will tell if this hold up to the heat generated inside the cabinet.


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