Hello everyone, its been a very long hiatus for me in these parts. Long story short - Work/Life/Health and other things have gotten in the way and then throw the Covid Pandemic into the mix...has all been a bit of a blur.
I wanted to share my recent addition to the fleet and this set is going to look very familiar to everyone. In New Zealand our native Thorn colour sets were basically cloned from various English models. So this is basically a Thorn 3500 - but the chassis was known here as the TX574.
I have been looking for one of these for over 20 years and I can say that this a very rare find as these all vanished years ago. So am pretty pleased with this find. It was a 10 minute drive from home and cost me five pounds ($10 NZD) The TX574 was also rebadged as an AWA Deep Image here as well.
They were disliked by most TV tech's due to their reliability problems and you guys would have been dealing with the same problems these were plagued with.
It is in remarkably good condition and last saw use in 1990's as there was a receipt card inside for a regun CRT around 1992. The plethora of service stickers on the back cover shows the amount of service calls it would have endured over the years. I forgot how heavy these sets are as needed a lift on one end to get it into the house and into the kitchen table.
This is the identical set I remember as a child except ours was a console. It was always breaking down and Dad threw the towel in with it around 1982. We traded it in on a National Quintrix which never broke down, but the tube wore out!
After some initial checks with a meter around the power supply to make sure these were no obvious shorts and after bypassing the open mains switch I got daring and decided to gingerly apply some mains and lo and behold the dam thing sparked into life after its 30 year slumber! Has issues as to be expected - vertical issues and no sound and lack of blue drive but I could see snow in behind all of that. I'm amazed it just didn't go bang!
Was able to capture some photos of it going before I saw smoke coming from the Field/Sound board so it got switched off pretty quick after that. I'm suspecting dud/open electrolytics is upsetting the frame stage operation causing the green dropper resistor to consume a few more watts than it should hence the smoke! The no sound issue is due to the speaker's voice coil being open.
So that's pretty much where I'm at with this. Not sure when I'll be able to do any further tinkering on this properly as its now in stored in a room where it can't be worked on but first light shows a promising start but then I know that the power supply/line stage will be the next areas to play up as there's lot of old caps, out of tolerance resistors and old silicon waiting in the wind to challenge me.
Unfortunately I have 'zero' spares/boards for this so will have to tread carefully. I have all the circuits/service info/fault lists in paper form so not completely in the dark!
Enjoy the photos 🙂
Glen.
@glenz75
There is a lot of experience of the 3500 chassis on the forum, lots were rented out in the early 1970’s. Unfortunately I have none, the small shop I worked at had a few dealerships but not Thorn. I had enough fun and games with those makes so perhaps not missed too much.
The set looks on very nice condition.
@glenz75 What a superb set, appears to have been well cared for. I see it appears to be fully isolated as I believe was the norm down under with that big mains transformer and looks like the one on the PSU has been deleted. We did see this over here but only on special schools receivers so that VCRs and the like could be connected, it was designated 3700. Your IF panel will be a bit different to over here and what type of varicap tuner is it fitted with?
I’m also about to embark on restoring the slightly earlier 3000 Mk2 so we can swap notes. Shame about the loudspeaker as it’s a rather high value at 80 Ohm, probably a difficult one to source even here.
The 3000/3500 is my favourite chassis to work on and have many in my collection. I look forward to following your exploits with it.
The TX500 series was Thorn's export chassis, it was discussed at VRAT in mid 2021. That centred around a Spanish market set that emerged using the TX500 series chassis. You can read what was said and see that here.
https://www.radios-tv.co.uk/community/colour-television/spanish-thron-3500/
Some useful Radios-TV links you may or may not find of use.
https://www.radios-tv.co.uk/vintage-electronics-blog-forum/30003500-circuit-description/
https://www.radios-tv.co.uk/vintage-electronics-blog-forum/brc-30003500-diagnostics/?seq_no=2
https://www.radios-tv.co.uk/vintage-electronics-blog-forum/brc-thorn-30003500-psu/?seq_no=2
https://www.radios-tv.co.uk/vintage-electronics-blog-forum/servicing-the-brc-30003500/
https://www.radios-tv.co.uk/vintage-electronics-blog-forum/set-up-eht-thorn-30003500/?seq_no=2
https://www.radios-tv.co.uk/vintage-electronics-blog-forum/brc-3000-panel-actions/
Thanks Frank - I know I'm in safe hands here with the knowledge and expertise here, gives me some hope that I should be able to get this set running to the point where it can be used 🙂
Hi John - Yes the set is in very good condition considering this would have ended up getting scrapped otherwise. Interesting re the 3700 chassis being isolated, I'm guessing this is what the NZ version was copied from. And you're right there is a transformer missing, I only just noticed that when comparing photos to one of Chris's 3500 sets. I'm not sure what type of varicap tuner it uses but when I'm next inside will take note and mention it. Good luck with your 3000 and I'll attempt to follow the progress. Getting a replacement speaker is going to be a problem, I would have had some of these years ago from sets that were scraped before I got to them, but biffed them out in a move some years ago including some spare reconditioned power supply modules/line output/timebase boards etc. Boy do I regret that now!
Chris - Thank you so much for all those links and very interesting reading about the Spanish export version, maybe this is what my TX574 was based on. I'm pretty sure I'm going to be needing the links as reference when I make a proper start on this beast and your efforts for the documentation and blog posts etc including and everyone else's contributions here regarding the 3500 is much appreciated. Not sure when this will be but hopefully soon. Will post up my progress for sure. Wonder how much swearing will take place as I work way through this? 🙂
