Ferguson 3173

Looks like I have a duff focus pot
But still not sure about the EHT tray because the picture looks lacking in something
So bad focus ,no red drive , no colour & these are only the faults I can see so far
These sets don't seem to far well with storage
While there doesn't seem to be any evidence of damp it's becoming clear that
It hasn't been stored in dry conditions probably been in a garage for years
But is so clean inside

Chris ( crusty tv ) can I take you up on your offer of an EHT tray ?
Just In case I'm barkin up the wrong tree here with the focus fault

Chris

Chris ( crusty tv ) can I take you up on your offer of an EHT tray ?
Just In case I'm barkin up the wrong tree here with the focus fault

Chris

Hi Chris,

I checked the box and what I thought contained about x20 8500 EHT trays, contained all 8000 EHT trays. Flamin typical as I have 8500 and 8800 sets and not one 8000 TV. I don't believe they are interchangeable due to the different focus arrangements on the 8000 compared the 8500/8800. I will have to do some reading on the service data to be sure.

As suspected.

The Thorn 8000 series line output transformer develops the full EHT AC voltage, hence it does not require a tripler. The 8000 EHT trays are rectifiers. The difference between the 8000 tray and the 8500/ 8800 tray is that the latter includes a resistor which feeds the focus pot, the former does not.

Did you measure the thick film units resistance what were you findings? Did they differ with regards to the expected values I gave above? I would lay money on it being the Focus control. I wonder if there is anyway you could lash up some suitable rated stand alone resistors to mimic a mid point setting to prove the point.

As for storage of these sets, mine came from being stored in a tin shed and although dry the humidity factor played havoc with transistors, IC's and almost all pre-sets. Legs of transistors and IC's were rotted.

Hi Chris

I did measures the focus pot
Between F & + I got 30 meg and between F & E I got open circuit
Which would meet the focus is floating
But the focus voltage is still low
I removed the spark gap & replaced the 100k & the cap on the CRT base
But still no joy

Chris

Well the focus is still poor but taking apart the focus unit & cleaning it did make a
slight difference
The lack of red is due to no drive to the red output transistor , looks like it's down to the
Mc1327 Ic being faulty
Another fault is the whole picture looks week as if the CRT is poor , now I know the CRT is good as all guns read over 90% on my CRT tester
I'm thinking lack of EHT & that would count for the poor focus too
I've managed to order a EHT tray & a mc1327
Then there is still the no colour to sort out
Now I know why I don't like thorn sets .
Give me a good old PYE any day

Chris

Now I know why I don't like thorn sets .
Give me a good old PYE any day

Chris

Noooooo...... even Pye's can be a pain in the posterior.

You will soon be the Thorn Master !!

Hi Chris, something to beware of if you have problems with focus on the 8500/8800. Although the focus controls do give trouble the paxolin of the CRT was known to absorb moisture if the set has not been used for some time, becuase of the high resistances in the focus chain the moisture can cause the focus voltage to be pulled down.

Watching the screen apply plenty of heat from a hairdryer to the print side of the CRT base PCB around the focus pin and spark gap, keep rocking the focus control and if this is the case you should start to see some improvement but it may take a while.

I'm afraid I was never impressed with the 8000 series sets, reasonably reliable but the 17" with it's unipotential CRT wasn't great, the 19" sets were acceptable but the 22" 8800 was a poor performer, built down to a price I suppose. The later 5 IC decoder did give much better and consistent performance in weak signal areas over the 3 IC type.

In D.E.R. we even had the model 5723, a 22" (A56-120X) version of the 8500 which of course had no pincushion correction incorporated in the design. It was dreadful

Now the later quirky 9800 chassis with it's odd inertia PSU kick start I thought was a much better set but it seems most engineers hated them.

John.

19" sets were acceptable but the 22" 8800 was a poor performer, built down to a price I suppose....

Now you've got me worried, I have one of those making its way up the queue for bench time.
https://www.radios-tv.co.uk/1975-hmv-2725/

Don't get me wrong Chris, they were reliable, predictable but in my opinion a bit lack lustre compared to a good 3500 and the competition at the time. Now the 9800 which was developed from the 8800 gave a cracking picture.

John.

I can remember when I first started in the trade, I was "seconded" to our field engineer for a week or two fairly early on.

Anyway we called out to a customer with a rental 8800 set, the complaint was poor focus, the field engineer unplugged the chassis return of the focus unit and switched the set on, after a brief sparking and crackling from the set he switched the set off and replaced the chassis return lead, the poor focus problem was fixed.
Now I don't claim to know if this was bodgery at its finest, nor do I recommend doing this, but it was just one of those things that stick in ones mind.

Don't get me wrong Chris, they were reliable, predictable but in my opinion a bit lack lustre compared to a good 3500 and the competition at the time. Now the 9800 which was developed from the 8800 gave a cracking picture.

John.

Ahh now you've hit my sweet spot.... my favourite chassis to work on is the 3000/3500. What's your opinion of the 9600? I have one of those also waiting in the wings. I've almost got all the early BRC/Thorn just missing a 4K ( desperate to find one) ,8K and 98K though I turned down an offer of a 98K as it ventures into the wrong end of the decade I'm interested in.

The 9600 series is a wonderfully over-engineered set capable of good results. The 4000 like the 9800 has a poor reputation but I would love to do battle with one, if one did pop up I suspect it would be well out of my reach. We live in hope.

The sourcing of the troublesome Thick Films units would be a problem though.

John.

I always thought that the 9k and 9k6 sets gave a reasonably good account of themselves, we only started scrapping them when the tubes were completely knackered or if it was going to take too long to fix.
most customers at the time were quite happy to hold on to them.

The 3k and 3k5 were getting long in the tooth by then and were more or less scrapped on sight, the replacements being the TX 9 or 10, the TX100 was a brand new chassis at this point in time.

Edit: never had any dealings, nor even seen a 4k set so cannot comment.

I worked for an ex Thorn engineer (ex D.E.R), and he swore by the 3k and 3k5 sets, he reckoned after the mods were done and they were set up correctly they were the most reliable sets.

He was bolloxed though with anything after the TX 10 , I fixed all of the later sets

Hi Andrew

I still prefer pye sets, never really liked or wanted a thorn set it came with some other
Sets I bought I was going to offer it as a swap for something PYE but thought I would give it a go
I know PYE can be troublesome the 170 series with that poor lopt to say the least
Personally ITT was the make I was raised on & still think they are one of the best
Hybrid sets ever made

Hi John

Nice to,hear from you again , hope your keeping well ,thanks for that information about
The CRT base funny you should mention that though I did notice that the focus changed
as the set warmed up
Thinking this could be down to the EHT tray I've ordered a new one anyway
Don't really like thorn sets probably because I never had a lot to do with them
Only ever seen the odd 3500 , 8500, etc but as I sad above ITT was my thing
But now I'm in to collecting anything PYE due to room restrictions I had to make a choice
This came as an odd set with some other things I bought together with a kit set
A Forgestone 1970's set that works fine .
So I now have a grand total of 4 colour sets 2 PYE's & the other 2 as mentioned
I'll give it a go with a hairdryer & let you know how it goes

Chris

Had loads of 8500 series receivers out on rental during the 70s, mainly the attractive Alba version and also the Marconi 4713. These sets were bought from wholesalers. I liked them, the sets didn't give too much trouble and the main thing these sets were liked by the customers.
The chassis morphed in the 8800 series which again wasn't too bad either but that 9800 thing, that was something else. That one is best forgotten.

Till Eulenspiegel.

Hi Andrew

Personally ITT was the make I was raised on & still think they are one of the best
Hybrid sets ever made

Chris

Back in 1984 when I did work experience at Cotton TV rentals in Peterborough, I can remember a chap called Steve Kruger telling me that ITT CVC5,9 were once the bread-and-butter set and could be installed and forgotten about.

Funny how that stuck in my mind.

Well back to the 8500 , had another look at the set today took the focus unit apart
Cleaned it baked it for about 20 mins on a low heat ( yes you read right ) I put the thick film part in the oven just in case any moisture had been absorbed.
When re assembled I had a clear focus we will have to see how long it lasts
While setting the set up for brightness I still thought the picture looked very week
Lacking in contrast , it still has no colour , no red drive & no sound
The only conclusion I can come to is that someone before me had switched the set on
After being stored in damp conditions & it flashed over taking out the line output transistor, & all three I/C's on the decoder .
I ordered replacements together with an EHT tray so we will see what happens when
The parts arrive

Chris

Well back to the 8500 , had another look at the set today took the focus unit apart
Cleaned it baked it for about 20 mins on a low heat ( yes you read right ) I put the thick film part in the oven just in case any moisture had been absorbed.
When re assembled I had a clear focus we will have to see how long it lasts

Chris

Funny you say that as I seem to remember the place where my dad worked had an 8500 in the cold and damp canteen.....
Often the EHT would crack over and the picture out of focus until it had been on a while and the set warmed through a little.

Well after the oven treatment for the focus unit all seems well even after a night in my garage
Don't know if you can get a good idea from the photo but that's the stage the set is at now
The low contrast , no colour , washed out picture

Chris