The Saga part 2

[csp]

This stupid donated desk has really got me stumped and seems to go against my 70+ years of electrocic knowledge (especially audio related).

As a recap, when the desk first arrived (May 2022) it would not work and on removing the base and cleaning all of the ribbon cable I discovered that the LEDS on the DSP and Brain Board were wrong. The DSP required only the Red LED although some desks have the Red and Green LED, this desk had all three (ie yellow as well) meaning a complete failure of the card. The Brain Board that requires only the Red LED had had all three LEDS indicating that the Board could not find the Eprom.

After much cleaning and the purchase of a new board and the manufacturing of new ribbon cables, etc the Brain Board suddenly and finally worked perfectly and did so for the next couple of years until I gave up about last Christmas after which I wrapped it VERY securely in bubble wrap and placed it in the cardboard box that it was received in --- the box then being fully sealed and placed in my garage along with the CPU unit that was similarly wrapped and packed.

During the 2 + yrs that I was working on it at various times the DSP board would work and so did the desk then for no reason the DSP board would stop working and would not show the correct LED combination.

Hence why I gave up !!!!

A few days ago I got the desk out and set it up in the spare bedroom (where I was previously working on it), and before turning it on I flipped it and removed the base. On booting to my surprise the DSP board's LEDS were perfect, BUT for some reason the Brain Board that had been working was now faulty in that it was showing both the Red and Green LEDS, indicating that the Board could see the EPROM but could not read its software.

HOW could this possibly be when it was the Brain Board that was previously working correctly and it was the DSP board that was faulty ???????

I have since cleaned all of the ribbon cables going to the Brain Board and checked their continuity, I have cleaned and checked both the Big Power plug and Data cable --- all is OK. BUT still the Brain Board is showing both the Red and Green LEDS. The DSP Board is still perfect. I have also removed and cleaned the clock card (currently using the Mackie card as that was the card last installed --- sometime last year).

One thing that I have not previously checked is the voltages going to the Brain Board, so to get the correct pin/voltage connections I looked up the service manual and found something that I have not previousluy noted (as I haven't previously checked the voltages on that plug). What does "MGND" stand for --- I understand the GND but what is the "M", as the connection just goes from the power plug (J41) to each of the three fader bank connections ?

If anyone can supply any suggestion/s to solve the problem it will be greatly appreciated as I am super fast running out of ideas --- again !!!!!!!

An Addendum.

I have just re booted the desk after posting the above and forgot to say that now the faders are randomly shimmering and if I put my hand under the desk and simply touch (doesn't matter how softly) a fader's knob that fader goes balistic, both physically and on the external monitor This has not previously happened.

This time I only had the desk running for about 5mins when suddenly it sounded as if all of the faders had jumped to the top and then returned to the bottom --- to fast for me to register the movement (possibly about 1sec) it was just the sound that I was aware of, again this is a first !!!!!!!

Any ideas why this new situation would suddenly start after the desk had been packed up for about 6 mths.

David

[csp]

Hopefully by tomorrow night I will have some VERY good news on the desk. It has been working perfectly for about the last 2hrs playing all 24 tracks from various songs on the HD24.

The perceived problem with the Brain Board having the Red and Green LEDs showing after reading much of my long post on the desk today to see what I had said about those LEDs, I discovered that the Brain Board should in fact have both of those LEDs showing. During this latest attempt at the desk I had not put a mic or any other audio signal through the desk --- had I done that the first day I would have discovered that the desk was actually working.

Being up side down I can't try things like the effects, automation or the transport section, but if all goes OK I will try those when the desk is the correct way up.

I will constantly try the desk for the next week and if no failings, I will take it back to the Centre, install it and see what happens !!!!!!!

The only problem being that for some reason (something that I have not previously experienced with this desk and definitely not with my own desk), on the external monitor the faders are randomly jumping to various level positions, including going straight to the bottom and staying there while the HD24 is playing --- the faders on the desk are not moving when this happens but are staying at the position that I set them with a long stick (can't reach under the desk without lifting it). Moving the desk faders to a position moves the external monitor faders to the same position as it should, but then the jumping of the faders on the monitor starts. Being in the desk's normal pre fader VU mode, when the monitor faders go to the bottom the monitor VUs still show the correct signal --- I can't see the meters on the actual desk and as I haven't as yet connected any speakers I have no ides if the sound on a channel that is jumping also jumps the speaker volume for that channel --- will connect some speakers tomorrow to check.

Because I haven't previously experienced this I really have no idea what is causing it or what the fix would be.

Wish me luck tomorrow and if all OK with the desk upside down, I will put it correct way up with the base on and see what happens because previously the desk often worked perfectly upside down but failed soon after being the correct way up --- I have no idea what plug or whatever could be breaking contact when the correct way up !!!!!

David