CurtPalme.com Home Theater Forum

[psilvest]

Hi there,

I finally managed to find the time to re-assemble a late M9000 that I had dis-assembled completely for a thorough cleaning several months ago. I put it all back together (except for the CCM) and powered it up, but I got a problem. The fans started normally and I could also hear relais contact noise at the moment of going from stand-by to power on, and then again 2 -3 seconds later (but no crackling noise typical of HV supply). No LVPS nor CLM diagnostic LEDs remain on, the tube filaments are lit (P14 measured to be 6.4 V), all would seem ok, but there is no sign of life whatsoever on the faces of the tubes.

I re-checked all the connections and found that, in the rush to finish, I had connected the HV wires to the HV splitter incorrectly - I had swapped one of tube HV cables with the HV cable from the HVPS. However, fixing this has not changed the situation. I have now swapped the LVPS with a spare one, but this has also not made any difference.

I suspect a failure in the HVPS, perhaps as a consequence of the initial mistake with the splitter wiring, but before swapping that too with a spare I would appreciate any suggestions about how to proceed.

Thank you,

Pier

[Curt Palme]

It doesn't matte what way you've connected the leads to the HV splitter, they are all tied together internally.

I'm guessing problems with the HVPS, HDM, CLM or VIM. Possibly a neck board as well.

Any of those can cause a 'no HV' condition without showing an error code on teh back.

turn the set on and off twice in a row to see if an H fail comes up. Sometimes it will only show once you power up the second time.

A V yoke wire connected by 1 pin off will also cause a no pix condition, but should show a V fail error light right away.

[Curt Palme]

It doesn't matte what way you've connected the leads to the HV splitter, they are all tied together internally.

I'm guessing problems with the HVPS, HDM, CLM or VIM. Possibly a neck board as well.

Any of those can cause a 'no HV' condition without showing an error code on teh back.

turn the set on and off twice in a row to see if an H fail comes up. Sometimes it will only show once you power up the second time.

A V yoke wire connected by 1 pin off will also cause a no pix condition, but should show a V fail error light right away.

[Nashou66]

Make sure you have the ribbon cables for the VDM connected properly, one row off it wont start, one pin off to the side and it can damage the VDM.

Athanasios

[psilvest]

Thanks for your fast replies.

Indeed after turning the set on and off twice in a row the H fail LED comes up. Does this mean a failure in the HDM?

The ribbon cables seem connected ok.

Pier

[psilvest]

I have replaced the HDM with a spare one and now the pj is working... well, almost working, since the blue tube still shows no sign of life (red and green are fine). I rechecked all connections for the blue tube, all seems ok. Also, the filament is lit.

I have excluded problems with the VIM (swapping blue and green cables at the VIM makes no difference), the VIM blue cable, and the blue neck board, which I swapped with the red one (again, no change).

Any suggestion as to what to check next?

Can I swap tubes without damaging anything?

Thanks

Pier

[draganm]

[Nashou66]

[Curt Palme]

[Curt Palme]

[draganm]

[Nashou66]

I think the newer ones are just better insulated.

Athanasios

[psilvest]

I swapped blue HV with red HV at the HV splitter, but there is no change - problem is not there.

I am thinking of swapping blue and red tubes to see if there is anything fundamentally wrong with the blue tube.

Is there any test point where I could check for correct voltage, for instance on the neck board?

Pier

[draganm]

Pier take a look a tthis thread
https://www.curtpalme.com/forum_archived/viewtopic.php@t=19735.html
very similar problem with flaky blue tube. If you already swapped neck-boards, then swap just the thick Black G2 wire to rule out the HVPS G2 feed. Failing that, The tube might simply be dead. Check the voltage across P14 at Motherboard, if higher than 6.35 tube filament might be stripped

[psilvest]

Thanks Dragan, but I had swapped blu and red tubes before reading your post and concluded that the problem is with the blu tube, because the red tube works fine in the place of the blu, while there is still no sign of life from the blu tube. I had already checked that the neck boards are ok and that heater voltage is also ok. The tube does not have many hours and its emission should be as good as that of the red and green tubes.

I have now closely inspected the tube and I fear a problem with the HV cable / anode cap (everything else looks fine). I noted that the HV cable was strongly twisted inside the tube plastic case, such that it was sharply bent at the entrance of the anode cap. The mechanical connection between the cable and cap feels rather weak and the cable can be flexed very, very easily. I wonder if there is still an electrical connection with the tube anode, but I do not know how to verify this without removing the entire cap (as shown in http://www.curtpalme.com/HV_Lead_Removal.shtm ). I cannot see any other reason for this tube going dead.

Pier

[draganm]

[psilvest]

It seems I was jumping to conclusions too quickly about the reason for the apparently dead blu tube. I have checked the continuity of the HV connection by putting a needle through the centre of the anode boot to reach the clip, and continuity is oK, to my disappointment.. (I covered the hole in the boot, even if invisible, with a good dose of silicon to avoid HV leak). Also, a capacitance exists between HV lead and the aquadag lead, like on other (good) tubes - if the HV connection were broken, capacitance should be zero (I could not precisely measure it, it is below the sensitivity of my Fluke 179, but seems to be there).

To recap:
- the tube gives no light (except for filament..)
- another tube in its place works fine
- the tube is 'young', with no sign of wear, burn, neck browning, damaged pins,..
- HV connection seems OK

Is there anything I could check further? Is somebody with a tube tester my only chance to find out what is wrong?

Thanks

Pier