HP 1630A/D/G display driver board. Help, please/

[MouldyOldGit]

Hello All,
In a drunken moment, I bought a broken HP1630G logic analyzer boat anchor on Ebay. Unit powers up, but display is totally bright with no inkling of expected output. All power supplies are good. Expected signals are present on the connector to the display driver board. CRT cathode, which should be 40-80V relative to G1, measures around 4V. This explains the bright display. Disconnecting the cathode results in a blank display, so I don't think there's a permanent short in the CRT. There's no schematic for the display driver board, which was supplied by Hitachi.  There are two resistors of which I am very suspicious as they seem to be open. These are R229 and R761.  The attached (poor) photo shows them. They are the components with one end soldered to a standoff so they they slope up off the board. There are no decipherable colour bands. Can anyone with a working 1630 (or a 54201 'scope) possibly help me identify these components and the correct values? 

Thanks in advance,
MouldyOldGit (a.k.a Steve)

[SoundTech-LG]

Hi,

I have a few of those display boards sitting around collecting dust, so yes, I'd bee happy to check on this for you. Won't happen for about 7 hours from now though. I imagine you'll be getting ZZZZZZZZZZZZZZZs
by then.

[MouldyOldGit]

That'd be brilliant, thanks! 

[SoundTech-LG]

No problem. I'll post the measured values...

[SoundTech-LG]

Ok, I have 3 accessible boards, the rest are inside equipment. Not sure this will help you though. All 3 boards have R229 more toward the center of the PCBA. R761 is close to where you show it. All the boards measure roughly the same at those in-circuit resistors R229 = 56 ohms,
R761 = 2.4 ohms. Also... they are not slanted to the board on the vertical metal post, instead, they used longer leads as some heat sinking. One board has HP part # printed in black on the board 2090-0131, and it also has a label on the aluminum aluminium? plate with Hitachi model#CDK-10BA242. The other two boards are both HP part #2090-0104 in black, (no label). All 3 appear very similar.

Look at these photos... they are the same as what I have. One photo shows R761.


https://www.ebay.com/itm/402343849742?hash=item5dad8fef0e%3Ag%3A%7Ez8AAOSwy2BeAHew&LH_BIN=1

[MouldyOldGit]

Thanks for that, I'm very grateful to you for going to the effort.

Looking at the values makes me think that these are rather more like fuses, possibly in case of an inter-electrode short in the CRT. In which case, mine may have had an intermittent one, given that both were open. Ho hum.

Anyway, I've substituted them with two reasonably beefy resistors and the screen comes up to reveal garbage, so on to debug the CPU card...

Once again, thanks.