Solved HR Diemen 7370 LOPT

[cools]

A while back I picked up a bunch of different Hantarex Polo chassis - sold as working but not shown as such. Usual caveats, they were a fair price even if they possibly would need repair by an expert rather than me.

What I'm curious about is that two of them (a Polo 25 and a Polo 28) had their LOPT replaced with a HR 7370. There's some signs of life - the 25 degausses (while throwing a spark at one end of the fuse) and the 28 makes a slow clicking sound, but neither have the grey wire that comes out of the smaller/second transformer connected to anything.

Line Output Transformer / Flyback: HR7370 (HR 7370) - 12420178 ELDOR MONITOR LINE OUTPUT TRANSFORMER (LOPT)/ FLYBACK... - UK (GBP)

hr 7370, 12420178 eldor monitor line output transformer (lopt)/ flyback 28029390

www.donberg.co.uk

Should the wire be attached anywhere? Are these even a suitable replacement? The pinout doesn't seem to match a HR7381 and the chassis themselves don't appear to have any modifications, so I'm wondering if someone in the past fitted them while praying they'd work.

 

[M K L]

HR7370 is for the Polo 25"/28" 25KHz, not for the more common 15KHz version. The 25KHz version (which can do 15KHz as well) has vertical modules for poly caps behind the flyback and uses a tube with a low inductance horizontal coil (same as a 31KHz tube). The external block contains the HV smoothing cap (across anode and ground) that you can see in the diagram in the link you posted (sometimes it's built in the flyback body). If you're not sure post pics.

 

[cools]

Here they are. I don't see anything different to my working ones around the flyback area.

 

[M K L]

That's a 15KHz Polo so 7370 should not be used on that.

 

[cools]

Thanks, confirms my suspicion that they were fitted in vain. I'll use them for some desoldering practice.

 

[tb2000]

Yeah I can't imagine how they'd even have worked at any point with those in! They should have HR7191 in them. HR7375 (usually found in the Polo 2 dual sync chassis) will fit and work ok too.

 

[M K L]

The people that know how to work on monitors are getting fewer and farther between.

BTW, the HR7370 fitted on your chassis is the newer (= China made) HR production (sold by Tecknoservice), qualitywise probably not on a par with the older production (e.g. the one in the Donberg link above). Although I haven't tried this myself, HR7370 could replace HR8068 on the Hantarex Polo Star chassis that do 31KHz (VGA/SVGA and 15-25-31KHZ ones).

I have just uploaded the manual/schematics for the 25KHz version on the Arcade Otaku wiki:
wiki.arcadeotaku.com/images/7/75/Hantarex_Polo_25-28_25KHz.pdf

 

[tb2000]

The HR7370 also apparantly fits the Polo 1 dual sync chassis (not auto switching). Not 100% sure but I think the last Polo 1 dual sync I repaired had a HR7370 in it which I had to replace at some point when it went faulty.
By the way M K L, is the HR Diemen site down permanently now? All that comes up is Efiter. Just wondering as to where to get lopt schematics now, apart from buying an original HR book+CD. Or is it on the Efiter website somewhere that I haven't found yet?

 

[M K L]

Yeah, looks like it's gone for good this time. No biggie, just use the wayback machine.

https://web.archive.org/web/20260103135100/https://www.hrdiemen.com/reparation/flyback/scheme/7370