Ferguson 3713 BRC8500 Chassis Restoration
I have up on the bench a pretty tatty example of a BRC 8500. Obtained a few weeks back. It looks to have been a quite high hours set with a fair few replacement components.
Initial checks revealed one of the big can electrolytics (700uf 250v) to have spewed its guts out and significantly dropped in value. after tacking in a temporary replacement and checking fuses i applied power. the set sprang to life with sound and an out of focus raster of sorts.
Only one channel selector works due to the usual Thorn tuner plastic rot. I managed to tune in my pattern generator and obtained a badly focused, mis-converged crosshatch. Then the frame collapsed.
I have currently stripped the set right down to clean everything carefully and thoroughly and re glue the top of the cabinet which practically fell apart. It was all in a pretty nasty fag stained mess.
A little more progress although not much. The tube and chassis is back in now.
powering up revealed a snowy de-focused raster followed by an intermittent frame collapse that sometimes opens up when trying to tune in a signal or tapping the LTB panel (dry joint?) The time base is also running too slow.
Any tips would be much appreciated
That's all for now.
Re frame: Dry joint does sound feasible but also check VT10, VT411, VT408, VT409, R457 and R458
Re line speed incorrect: Have you tried adjusting the Hoz hold performing the correct procedure? Short the two pins adjacent to the osc coil screening. Adjust coil for a floating-picture it should resolve when the link is removed. If its still not locking check VT403, VT404, C421, C423, C416, C414 and C445. Might be worth checking the discriminator diodes in the flywheel too, W405/6
If you've a scope then it wouldn't hurt to scope the osc output to see just how far out it is. Been there, done that and got the T-shirt recently with my Ultra osc being way off and unable to lock up due a leaky, high ESR out of value decoupling electrolyctic.
Best to get the frame sorted out before worrying about the line as with the frame fault fixed you then might then be able to see if you have frame lock but not line. If that is true this could be due to VT405 faulty or the reference pulses fed to the discriminator missing.
Also worth checking and reporting all your rails.
Re your contact about a service manual: As a gesture of good faith I'll sort out the service manual for you as a one-off. As I said in the e-mail, access to data for members of Radios-TV is via a rewards system and earning points as detailed here.
Edit:I also note you've posted this same thread across three forums, hopefully you won't get too much conflicting advice that may confuse you. Also I hope you understand the data when supplied is only for your use and within this forum.
The manual is scanned however its rather too large to e-mail and your e-mail provider rejected it. I will have to think of another way of getting it to you, do you have a private drop box?
The manual covers the 8000,8800A and 8500. The 8500 is virtually identical to the 8000 just with differences for the larger CRT, hence greater HT, focus and scan-drive requirements.
The manual is now in the TV data area for those members who have access and wish to play along with Jan's repair.
OK solution found, I totally forgot I have the ability to provide members with their own e-mail address and additional storage space on the server.
I can give members an an e-mail address email@example.com (where xxxx is your choice) which has a 2GB (easy web front-end) inbox and with that you also get a 2GB personal online storage for files another web front-end for management. As I say both have their own web front-ends to access. Uploading and downloading files to the online storage couldn't be simpler with drag and drop or broswe local and upload.
A half decent picture at last! Still needs a proper purity/convergence/greyscale set up.
The 25v rail was way down at 18v. Went through the right procedure in the manual to set that up and its now rock steady at 25v.
The frame collapse was down to a dry joint or a dodgy connector? The transistors in this stage checked ok. after re-soldering a few suspect joints and plugging everyting back in i had full frame.
The Blue and Red static magnets had also seized so these have been freed up and the magnets glued back into the handles.
The CRT looks a little bit weak but may come up after some use
had it on soak all afternoon and it seems quite steady.
The decoder seems to be working now after a few tweaks and cleaning the presets. Will still probably need setting up properly.
The purity is awful as is the convergence and greyscale so i think that will be the next chapter.
I quite like these little sets, I was lucky in that mine came with its stand. Not so lucky in the CRT department, the red gun is all but conked out. However I do have a NOS replacement just not got around to swapping it in yet.
Look forward to your next update.
Your set looks fantastic! Even with a low tube. The cabinet is certainly in better nick than mine. The stand is a nice touch too. I would have expected it to be a pedestal type a bit like the 18" Decca Bradford?
Gave mine a quick and dirty purity and convergence this morning. The glue on the magnets set well overnight. Its safe to say the tube is way past its best but still perfectly watchable. Also, the blue lateral magnet seems to have no effect whatsoever.
Just the channel selector to be re built now and i may get some form of fablon to re-do the cabinet as its in a real s**t state. Almost looks like its been dragged along gravel on one end. All in all, Not a bad result!!