1975 22" HMV 2725: Thorn 8800

That looks absolutely superb Chris, you've well and truly nailed that one. Excellent result. 

Chris said
The snow was really snow if you know what I mean, before hand it was very lacking. I tuned in and well, I will let the pictures do the talking.  

A very important observation, never just go with one symptom look and listen to them all and you will reap dividends.

Chris said
Paid a visit to the premier Colour telly spares shop in the North East, namely Malc's Speedy Spares. Who cares if CHS has closed, they couldn't begin to come close to the stock or speed of service  MSS offer. I collected a spanking new Thorn TX100 UHF tuner module also had a good chin wag about TV's as you do whilst watching the torrential rain we're having up here.

Needless to say I hurled the the old module and its now firmly embedded in the back fence of the garden.

Is it on soak test? 

John.

From an unpromising start, a nice set there.

Now; can we please have something that's got some valves in it - please?! All these semiconductors are doin' me 'ead in!

This set does intend for me keep giving it attention.

I noticed the other day the green static was very temperamental but it slipped my mind. This evening I was doing some final tweaks to the convergence as I had noticed some errors on the TCF and when using the pattern gen. Whilst performing the static the green knob/magnet decided it was not going to turn but not before it turned enough to put it all out leaving no ability to rectify. The problem, the magnet had come unstuck from the knob. Little else for it but to dismantle remove, glue and try tomorrow when its set.

This self same problem happened on the Fergy 3713 ( 8500)

Chris said 

 

Overall it looks to be all present and pretty much unmolested. When I swung the I/F-Chroma-Video panel out a large core dropped to the floor. I've no idea where this came from, its certainly not from the signals board or the convergence above, we shall have to wait and see. 

  

 Did you ever find where the core came from Chris?

No I checked all over and could find nothing that it would fit.

Just had an idea to speed things up. I've got a spare 8500 static yoke, they share the same static controls.  I will remove the green from that yoke as it working and use it in the 8800. When the 8800's one has set I can put that back in the 8500 yoke.

Chris said
No I checked all over and could find nothing that it would fit.

 I was wondering if it came off the line-linearity coil, only because to my eyes the picture looks slightly cramped towards the right (or stretched on the left)  with TCF displayed.

Just looked at the earlier pics of the chassis, and the linearity coil looks intact

The 8500 static control went in a treat, I did the static and tweaked the dynamic and I'm happy. That's it, I'm putting the back on this and its relocating to the TV display room.

The Borrowed 8500 Green static

Installed and the final shot

The CRT for how I found it, is giving in my opinion superb grey-scale and colour too for that matter. All in all not too bad for an example of the rarely seen 8800, a set a lot of the trade said should be forgotten. Its worth remembering this set has not been restored just repaired, its running with 90% of the original components including many 10's of tants.

And The body count?

Only 15 components were changed to get the set working......... Of course others may fail but that's why I like fix-on-fail.

The CRT seems to have improved with use, excellent picture on the set. 

Another superb repair Chris.

Frank

nuvistor said
The CRT seems to have improved with use, excellent picture on the set. 

Another superb repair Chris.

Frank  

Couldn't agree more.

Well worth the effort and a good addition to the collection.
 

PYE625 said

 Did you ever find where the core came from Chris?  

Sorry I missed that post. Its actually a spacer which is normally glued to the metal backplane behind the decoder. It's purpose I think was to prevent the print side from accidentally coming into contact with it.

John.

Jayceebee said

It's difficult to tell, I wonder if anyone else has spotted this but there is what appears to be a hint of poor LF response looking at the letterbox at the top of the testcard. This could again be many things possibly tuner or even just a tweak of the AFC coil.

John.

  

Hi John,

sorry to have not responded to this post of your, playing catch-up on posts I found it. Yes I see what you mean from the older shot of TCF. Its much improved now with the new tuner but still slightly visible on the final TCF picture above in post #128.

It looks pretty good to me now Chris but you could try this to see if you can improve matters, but before you do make sure the effect is there with differrent signal sources. Now this definitely is not by the book, it's based on experience and on VSB signals not DSB of a modulator.

If you switch off the AFC (by means of the control inside the tuning compartment, or holding in a tuner push button) can you improve it by a slight adjustment of the tuning pot? If so switch the AFC back on and adjust L111 for the best tuning point.

A tiny adjustment of L112 in the vision detector circuit might also produce some improvement. I don't remember the exact procedure in the manual but here's a method I discovered of doing it by eye. Simply add an attenuator(s) to produce a fairly noisy picture and adjust L112 for best definition, as I say not by the book and there may howls of protest but it certainly worked for me.

John

Friend of mine John in North London has a 17inch version that he believes is a prototype it looks identical in cabinet, from memory its an unfinished one, there is no remote receiver and no channel change buttons just neon's. I will be seeing him soon so will have another look.