Sony BVM D24 Overload issue
 

Hi,

I'm hoping there are some engineers and technicians on here who may have used or come across these amazing monitors in their work!

I have one I got during lockdown to watch movies and play games having got back into CRTs.

The monitor is in good condition, well used (60,000hours) and has a few bangs and marks but the screen is perfect and the picture truly amazing in person (and in a dark room!). I like to think it has a little bit of history as it has an Aardman Studios label on it - but I bought it in an auction so do not know the background at all. I just like to think it was used for Wallace and Gromit!

My issue is on start up (either a cold power on or powering it on using the controller from standby). The monitor will start initialisation but when the screen gets bright the overload warning light comes on and if I do not turn the monitor back off, the NEON overload bulb will flash and the monitor will shutdown to standby. If you turn it back on right away, it will initialise again but this time complete with no overload issue. I've had all the removeable cards (PSU, Deflection and Input) tested in a working monitor and the overload issue has not occurred, so my theory is I have an issue with the flyback or flyback board. I wondered if anyone had come across this issue before and might be able to offer some advice on a solution?

Although I can keep using the monitor, I don't think it can be healthy for it to keep overloading on every start up and I'd like to identify and fix the issue if I can.

I hope someone can help.

Re: Sony BVM D24 Overload issue
 

When it flashes bright upon initialisation, is the screen bright blue or red ? Or just bright white ? If it’s a particular, this would indicate a gun shorting on the CRT.
It’s possible there’s an issue on the PA board, though these are more fiddly to swap (worth checking the electrolytic capacitors of course).
The fly backs were generally reliable on these though there was a faulty batch on later serial numbers, which resulted in a distorted raster, rather than an overload issue. Unfortunately, all parts are long since discontinued and the factory closed in 2008.
The BVM-D24’s were the last of the grade 1 CRTs before Sony changed to lead free soldering with the ‘A’ series CRTs, and then it was LCD & OLED after that.

Good luck,
Retrotechie

Re: Sony BVM D24 Overload issue
 

Thanks, that's really helpful. I've taken out all the boards and sent them to someone who has a working D24 to plug them in and test.

The colour is bright white when the overload first comes on. As it progresses through the initialization it does turn slightly green before it finally shuts down (with a slight burning smell - I assumed this was from the neon bulb on the overload circuit which flashes before the monitor shuts down to standby - but this smell could be from a short?). I'm guessing a short on the Green gun would mean a new tube? So very much hope that's not the issue! Or if that is the issue might there be hope replacing or servicing the neck board?

It's weird that when restarting it will load without issue, I was hoping it might be a part going out of spec but after having some current going through it it was OK enough to get through the start up - but perhaps that's to do with the short being warmed up?

I didn't realise the A series was lead free, I wonder if they are more finicky because of this. Hoping I can get the monitor working as the picture really was amazing.

Re: Sony BVM D24 Overload issue
 

Given the tube hours, it would seem likely it is the CRT causing the overload issue
The smell will be the resistors on the neck board getting hot, as they (or at least one of them) is being shorted out. However, it is unusual for the green gun to go (but not impossible).
If you tap the tube with the handle end of a screwdriver, whilst the monitor starts up, you should be able to instigate the issue, and prove that it is indeed the CRT causing the issue.

Re: Sony BVM D24 Overload issue
 

A shorted gun will not be fine when you try again.

Re: Sony BVM D24 Overload issue
 

The issue I have found with these monitors personally is that when the CRT develops a short, it tends to be thermal, so switching on from cold, the issue occurs. After that initial period with the heaters up, is sometimes enough to clear the short between the cathode & grid of the particular gun that’s causing trouble.

Re: Sony BVM D24 Overload issue
 

Switch on faults were quite common on Trinitron tubes. A B&K 467 CRT tester can clear shorts very well, myself and other colleagues used this method many times on Trinitron tubes during my years with Sony.

Re: Sony BVM D24 Overload issue
 

I worked for Sony then but never saw one, I can't find the manual but were these grid or cathode modulated? Surely if they were cathode, running the set with each grid drive disconnected in turn would be a good way of finding out where the issue is. I assume the drive circuitry is on the tube base, simply desolder each cathode in turn. But good luck with it, always liked Sony CRT sets but some of the larger sets had purity problems,
Tony Walkr

Re: Sony BVM D24 Overload issue
 

I used to work for ST Microelectonics in Almondsbury near Bristol.

Aardman Studios were right next door to us and in the summer months we engineers would sit on the grass outside and observe the Aardman luvvies at safe distance. :)

Re:Sony BVM D24 Overload issue.
 

This is very good news to hear, and would make sense with the nature of the fault. I do have the service manual (located online here: https://ia600802.us.archive.org/0/it...e%20Manual.pdf), but haven't dug into the ability to either disconnect or desolder the guns to test for a short.

I do not have a rejuvenator / tester but have seen them on ebay from time to time.

I've had all the removeable cards and boards checked in another monitor and serviced (all passed with flying colours) so when I get them back I'll test if that has made any difference (likely not) and can move on to the gun testing. If anyone on here has a tester they may be willing to loan (or for me to bring the monitor to them) then please do let me know!

Thanks again for the help and advice :)

It is a small world! I bet there were some stories to tell from those days.

Re: Sony BVM D24 Overload issue
 

Hi Adam.

If you can borrow a B&K 467 when you connect it to the CRT (It must be cold) The shorts lamp will light up, pressing the "Clear shorts" you will see a short burst of sparks in the gun assembly and the problem should be resolved.

Re: Sony BVM D24 Overload issue
 

Thank you, I've put a post in the wanted section and hope they'll be a fellow enthusiast in the area! I'm guessing you take off the neckboard and disconnect all the cables, attach the tester to the tube and cross your fingers. I read somewhere gently tapping the neck with a screw driver can cure a short but I'd see that very much as a last, last resort!

Re: Sony BVM D24 Overload issue
 

I have not yet found a 467, but I have come across a Leader LCT-910A which I might try. Does anyone have any experience with these testers / rejuvenators?

Re: Sony BVM D24 Overload issue
 

I have a 467 which you're welcome to borrow, but I'm a bit far away and postage might be prohibitive!

Re: Sony BVM D24 Overload issue
 

Thank you! :)

I might be able to take you up on the offer as I am planning on taking the family to Wales for the half term break. How heavy is the unit? Up to 10kg is usually OK (about £10 each way). I'd much prefer pick up though as you never can trust the postal service!

I'll wait a few more days and see if anyone a little closer can help out before coming back to you.

Re: Sony BVM D24 Overload issue
 

Feel free to PM me if you would like to borrow it - I rarely use it these days.

Re: Sony BVM D24 Overload issue
 

Hi, I've managed to get a Leader 910 CRT tester. I'm not sure if it is as good as the B&K. Have you had any experience with this? It comes with about 10 different neck attachments (and a few custom looking ones!) how can you tell which one should be used? There is a guide / manual with the unit but it's quite old and the BVM was probably made after the Tester!