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Old 21st March 2010, 08:12 PM   #1
muizel is offline muizel  Netherlands
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Smile Help needed with Krell CD-DSP

Hi Guys,

I have a Krell CD-DSP and suddenly the remote control stopped working basicly the mainboard contains all vintage philips like the cdm1mk2 and the following chips:
mab8461,mab8441,saa7210,saa7220,and one chip i don't know called lattice gal 16v8a.

Krell made its own da converter board with its own audio output circuits wich is on top of the mainboard.

Everything works ok also when i use it as a separate converter. The rc receiver gives a signal on the scope and this signal seems to go through the lattice gal 16v8a but nothing happens, some other strange thing i noticed is that the safety ir eye (omron) wich sees that there is a cd on the table and switches the laser on is also not working, i tested this and the ir led and photo transistor are ok and the player play's the disc normal.

Another thing i noticed that when putting the mains on i have to switch the power button two times to get the player reading the toc and i can press play. When i let the power on and the player is in standby i reacts normally when i press play.

All the front buttons and the display work normally and all voltages from the ps are correct as far as i can measure without a sevice manual.

Anybody an idea to help me out i really love this vintage machine with it's beautifull perspex cover.

Thanks alot Rene.
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Old 22nd March 2010, 12:12 AM   #2
guido is offline guido  Netherlands
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This requires the service manual or quite some reverse engineering.

On the GAL, this is programmable logic. So you can put in whatever you like (e.g. AND, OR etc gates. Outputs can be latched). So you can't just replace this chip with another one as it will be either empty, or worse contain the wrong logic.

I've got these chips and a programmer, but can't help for now.

MAB's are the micro controllers running the player.

First check your powersupplies, start with the gal i guess.
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Old 22nd March 2010, 11:29 AM   #3
muizel is offline muizel  Netherlands
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Quote:
Originally Posted by guido View Post
This requires the service manual or quite some reverse engineering.

On the GAL, this is programmable logic. So you can put in whatever you like (e.g. AND, OR etc gates. Outputs can be latched). So you can't just replace this chip with another one as it will be either empty, or worse contain the wrong logic.

I've got these chips and a programmer, but can't help for now.

MAB's are the micro controllers running the player.

First check your powersupplies, start with the gal i guess.
Hi Guido,

Nice to hear from you again and thanks that you will help me. The gal gets 5 volt single and sits in a socket on top is a sticker with some code i gues krell did that, when i remove it from the socket nothing works cdm is not starting no display, i found out that the safety ir eye for cd on the table is also runnin through the gal. Had a look at the datasheet and saw that the i/o pins off the gal run through the opposite pins so what i tries was took some little jumpers and connected them and the player works normally exept ir reception and safety eye. What i also did is take a dive in old philips service manuals and saw that at most players the drawer open/close switch goes directly to the mab, and the ir rc signal also but when i do this with the krell ther is no respons i even changed both the mab 8441 8461 and that shuts down the player i guess that in the mab is also a little programming.

So that all i did for the moment and if it was not such a beatifull player i allreaday took it to the kringloop do you have any idea's by the way when using it as a single da converter the sound is very good i replaced the old opamps with LME49710 and the rest off the output is al discrete fets with good components

Do you have any idea ?


Thanks Rene
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Old 22nd March 2010, 01:58 PM   #4
muizel is offline muizel  Netherlands
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Help please
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Old 22nd March 2010, 06:00 PM   #5
guido is offline guido  Netherlands
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The sticker on the GAL shows which revision of software is inside, i guess.
I guess you tried to connect in and outgoing pins opposite of each other of the GAL? Problem is that you can define anything inside, so the opposite output pin could well be driven by not the opposite input pin. Or many of input pins, etc. Why it is used will remain a mistery untill you find the service manual or do severe re-engineering. Take it out and see what output reacts on what input, assuming the gal is o.k...

One of the GAL pins is a clock input to latch other outputs (if programmed to do so). You might check if there's a clock on that pin. Which would explain maybe a bit why the gal is there. Another option would be that it blocks certain signals towards the mab's during reset.

Swapping the MAB's is not a good idea.....! Yes, controllers contain code. Which sets certain i/o pins to input and certain to output. So you might have connected a controller output to other logic also set as output by swapping. And it's easy to destroy something....

Don't bring it to the kringloop, just sent it to me then
What type is it anyway?
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Last edited by guido; 22nd March 2010 at 06:03 PM.
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Old 22nd March 2010, 08:13 PM   #6
muizel is offline muizel  Netherlands
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Quote:
Originally Posted by guido View Post
The sticker on the GAL shows which revision of software is inside, i guess.
I guess you tried to connect in and outgoing pins opposite of each other of the GAL? Problem is that you can define anything inside, so the opposite output pin could well be driven by not the opposite input pin. Or many of input pins, etc. Why it is used will remain a mistery untill you find the service manual or do severe re-engineering. Take it out and see what output reacts on what input, assuming the gal is o.k...

One of the GAL pins is a clock input to latch other outputs (if programmed to do so). You might check if there's a clock on that pin. Which would explain maybe a bit why the gal is there. Another option would be that it blocks certain signals towards the mab's during reset.

Swapping the MAB's is not a good idea.....! Yes, controllers contain code. Which sets certain i/o pins to input and certain to output. So you might have connected a controller output to other logic also set as output by swapping. And it's easy to destroy something....

Don't bring it to the kringloop, just sent it to me then
What type is it anyway?
Hi Guido,

Thanks for you reply, I must say i am a bit sick off it i bought it a few weeks ago and everything worked ok. I will follow yor advice and see what comes out. I don't exept the sound quality off nowaday's but it is a sort off collecters item.


Rene
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Old 23rd March 2010, 12:04 PM   #7
muizel is offline muizel  Netherlands
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please !!!!!!!!!!!!!!! help
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Old 24th March 2010, 06:06 AM   #8
gto127 is offline gto127  United States
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Have you tried cleaning the sockets & IC's? I was told Krell cleans them with CAIG de ox it. Krell don't release any of their service manuals to the best of my knowledge. I know it will be a challenge. I have a CD DSP which I rebuilt & it sounds really sweet. I replaced all the red caps with Nichicon muse, I thought about changing op amps but didn;t know what type would be best. Hope you get your player going.
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Old 24th March 2010, 08:18 AM   #9
muizel is offline muizel  Netherlands
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Quote:
Originally Posted by gto127 View Post
Have you tried cleaning the sockets & IC's? I was told Krell cleans them with CAIG de ox it. Krell don't release any of their service manuals to the best of my knowledge. I know it will be a challenge. I have a CD DSP which I rebuilt & it sounds really sweet. I replaced all the red caps with Nichicon muse, I thought about changing op amps but didn;t know what type would be best. Hope you get your player going.
Hi,

i replaced the old opamps with LME49710 and that is a very good !!!! improvement it won,t cost you a lot and the sound is great.

When you switch from cd to da use only does the displa switch off that can help me with fault finding it is probably only one 10 cent chip wich is progarammed by Krell and they don't support it anymore.

I would so very much have him up and running again, oh the sockets are in good shape.

THanks Rene.
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Old 24th March 2010, 06:59 PM   #10
muizel is offline muizel  Netherlands
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