Sign in with
Sign up | Sign in
Your question

TAC scorpion meters failed... any scorpion/Amek experts??

Last response: in Home Audio
Share
May 14, 2004 1:22:10 AM

Archived from groups: rec.audio.tech (More info?)

>Hi, I recently bought a scorpion II... the LED and VU meters are all
>blown and are permanently peaked out. The previous owner told me the
>meters failed because the Amek 4091 IC's in the meter driver section
>failed. I managed to locate the replacement chips (at great expense!)
>but I wondered if anyone had any experience with this situation. My
>concern is that my rare and expensive 4091 IC's may fail again.... the
>previous owner of the Scorpion also told me that the meter chips
>failed when he hotpatched any of the group/monitor modules.... anyone
>heard anything about this? could some weird grounding issue be the
>problem on the monitor/group modules, or could it be a PSU issue?Any
>info would be greatly appreciated. Amek doesn't make the 4091 chips
>any more, and there is no substitute....., so when these ones die,
>that's it!..... thanks, Eddie
Anonymous
May 14, 2004 3:23:29 PM

Archived from groups: rec.audio.tech (More info?)

Hi there Eddie
A number of things in your post.
Don't put modules in or out of the desk with power on as it can spike all
manner of things. It is a trick done in the factory but they had a
bucketload of spare bits for the occasions when it goes wrong. Audio
patching is no problem obviously.
Check the power supplies in the desk. I have seen one with a failed
regulator putting 22 volts. It should be no more than 17.5 volts in the
desk.
There should be a resistor of 10K ohms or up to 100K ohms (preferable) in
series with pins 28 and 29 (analog inputs) to the 4091 chip. Although these
inputs are very high impedance when operating, a failure mode was identified
around the time of Scorpion manufacture where odd spikes on the input could
trash them. A series resistor cures this weakness.
The 4091 was custom made for AMEK and production ceased about 7 years ago.
If you are particularly nervous you could solder 18 volt zener diodes (5
watt) across the power rails of the bargraph boards having checked the
supply os 17.5 maximum.
Apart from some Mozart desks all others using the 4091 had the extra
resistors added.
I hope I have shed some light on this and wil gladly help if I can.
Best regards
Matt (Ex AMEK service UK....before Harman killed it!)
Eddie <thechococat@hotmail.com> wrote in message
news:84e54f48.0405132022.7619d5d9@posting.google.com...
> >Hi, I recently bought a scorpion II... the LED and VU meters are all
> >blown and are permanently peaked out. The previous owner told me the
> >meters failed because the Amek 4091 IC's in the meter driver section
> >failed. I managed to locate the replacement chips (at great expense!)
> >but I wondered if anyone had any experience with this situation. My
> >concern is that my rare and expensive 4091 IC's may fail again.... the
> >previous owner of the Scorpion also told me that the meter chips
> >failed when he hotpatched any of the group/monitor modules.... anyone
> >heard anything about this? could some weird grounding issue be the
> >problem on the monitor/group modules, or could it be a PSU issue?Any
> >info would be greatly appreciated. Amek doesn't make the 4091 chips
> >any more, and there is no substitute....., so when these ones die,
> >that's it!..... thanks, Eddie
Anonymous
May 16, 2004 5:43:09 PM

Archived from groups: rec.audio.tech (More info?)

>Subject: TAC scorpion meters failed... any scorpion/Amek experts??
>From: thechococat@hotmail.com (Eddie)
>Date: 5/13/04 10:22 PM Mountain Daylight Time
>Message-id: <84e54f48.0405132022.7619d5d9@posting.google.com>
>
>>Hi, I recently bought a scorpion II... the LED and VU meters are all
>>blown and are permanently peaked out. The previous owner told me the
>>meters failed because the Amek 4091 IC's in the meter driver section
>>failed. I managed to locate the replacement chips (at great expense!)
>>but I wondered if anyone had any experience with this situation. My
>>concern is that my rare and expensive 4091 IC's may fail again.... the
>>previous owner of the Scorpion also told me that the meter chips
>>failed when he hotpatched any of the group/monitor modules.... anyone
>>heard anything about this? could some weird grounding issue be the
>>problem on the monitor/group modules, or could it be a PSU issue?Any
>>info would be greatly appreciated. Amek doesn't make the 4091 chips
>>any more, and there is no substitute....., so when these ones die,
>>that's it!..... thanks, Eddie
>
>



I would defininately look at the power supply. One side of the supply is down.
ir prevented from supplying power to the board.

I had this happen on an old Studiomaster board and when the broken solder
connection was fixed, the led's operated normally.
Richard H. Kuschel
"I canna change the law of physics."-----Scotty
!