Lexicon 480L HSP Board Repair?

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mrclunk

Well-known member
Joined
Nov 29, 2006
Messages
1,191
Location
London
Our 480l is sick and i've isolated the problem to the 2nd HSP board.

It works but Machine B will freak out when changing programs and lock up.
Swapped the HSP2 into HSP1 slot and can repeat the problem. (you have to change a few jumpers to do this btw)
I've checked the psu and it seems in spec.

Any ideas or does anyone have a diagnostics cartridge i can borrow?
Who's the best guy in London for repairs?

thanks
paul
 
All the slots in a 480 are identical, you don't need to swap slots. All configuration is on the board jumpers.
If you have a faulty HSP, just pull it out. The Lexicon is smart enough to recognise its cards.
Once you pull it, you can only run one reverb.
I have recently supplied a diagnostic cart to Air studios, you could talk to them. I beleive they know a good Lexicon guy in London.
If you get stuck, I repair them, but I'm in New Zealand!
Most likely fault? Audio memory chips, unfortunately they aren't socketed, so its a messy job fixing them.
 
Simon Flynn is who you need for lexicon repairs
http://blag.proaudioeurope.com/index.php?id=49&catId=303
 
Thanks chaps, yeah I' m just running the one card at the moment.
Didn't realise you could swap slots without changing jumpers, have to try hsp 1 in slot two to rule out that possibility.

memory chip fault sounds like a good shout, I've read in other threads about dram faults.
with a bit of luck I might have spare chips, previous service guru was good like that!
 
So i installed new Dram and replaced U20/U51,  a lex service doc said the old Harris part could be problematic.
Anyway it was ok for a couple of weeks but is now freaking out again...

I can pretty much always kill it by switching machine B to patches within Bank 13.
I'm thinking maybe the patch memory is corrupt and thought i might be able to reload all the default patches via sysEx. But they're stored on eprom so no...

Does anyone know if the eprom reset trick for the Lex 300 works on the 480 eproms?
On a Lexicon 300
You may want to try resetting the unit.  To do this you will need to remove the EEPROM at board location U21 from it’s socket and short all of the pins to ground then re-insert the EEPROM (with the correct polarity) and start the M300L.  If this does not fix the problem we can set up a repair for the unit.
 
Have you checked the batteries on the processor board? There are two of them.
To do a reset, remove the batteries, or remove the battery backed ram chip.
One thing is that it still might be your HSP card. One way to check is make it a single card unit, and run it with only one HSP card. You dont need to change any jumpers. Just make sure you make it a single unit in the control section. If the unit runs reliably on one HSP and not the other, then its the HSP.
Problems on these can be very difficult......
 
thanks radardoug,
yeah i've checked it in single mode with one hsp and hsp 2 on its own. Its definitely to do with hsp 2. 
The eprom reset is just me grasping a straws really...

I tested the batteries before and they're fine.

I think i just got lucky when i 'fixed' it before, some sort of dodgy connection / cold joint / trace break healed and then hot / cold cycles bust it open? i don't know. Also the supposed 'NOS' dram i bought from the US clearly isnt.. The pins are cut and there's solder residue on them. Cost a fair bit by the time the import duty was payed.

The fault doesn't seem to be affected by high temperatures, its just when i start changing patches. I can have it on all day if i don't change patches it seems. It struggles more with the bank 13's large ambiences and bank ?'s delays. Possibly as they use more memory?

There's SDRAM on the board also but i did't change that as its very expensive and obviously i dont really know if its anything to do with memory in the first place!
Think i'll have to read through the service manual again and try to understand whats going on when changing patches.




 
Yes, they can be really tricky, not helped by the fact that Lexicon did not use sockets after their bad experience with the 224.
I had one the other day where I had to change all the dram a couple of times before I got it stable.
Most faults do seem to revolve around the dram.
 
No, sockets don't suck. Cheap ones do, if you buy good quality ones they work fine, and make servicing a whole lot easier.
The least Lexicon could have done was socketed the dram.
They had a bad experience with the 224 and Prime Times, where they used cheap sockets which caused lots of problems. Same with MCI and the JH24.
 
radardoug said:
No, sockets don't suck. Cheap ones do, if you buy good quality ones they work fine, and make servicing a whole lot easier.
The least Lexicon could have done was socketed the dram.
They had a bad experience with the 224 and Prime Times, where they used cheap sockets which caused lots of problems. Same with MCI and the JH24.

Well, everything I do is SMT and as such, sockets need not apply.

-a
 
Andy Peters said:
Well, everything I do is SMT and as such, sockets need not apply.
-a

Andy, if you don't use sockets, why are you dissing them?
I can tell you that by the time you have desoldered all the dram on an HSP board, you are very keen on sockets!
 
radardoug said:
I can tell you that by the time you have desoldered all the dram on an HSP board, you are very keen on sockets!

Here's the better question: why does the RAM fail to the point where it needs to be shotgunned from the board?

-a
 
Coz it's real old, and they didn't make those chips very well in the first place.
You will find that all the early dram is liable to be flaky.
Another favorite chip of mine from that era is the LS374, they seem to fail easily as well.
 
Success!

I don't want to count my chickens too early but i replaced all the DRAM and SDRAM sockets.
Also replaced SDRAM U13, 14, 26 and 27 chips.
The last load of dram received was clearly old and had been desolder so i didn't have a great deal of confidence in it...
NOS stuff in new sockets appears to have done the job.

thanks for all the help.

Incase anyone else is looking for dram, there's quite a few options for replacements. i ended up with hyundai chips.

Lexicon Dram that should work, Access time should be 120ns or under.

D41464C-10 (uPD41464C-10) NEC Electronics , Access Time (max) = 100ns
P21464-10 Intel , Access Time (max) = 100ns
HY53C464LS-10 Hyundai Semiconductor , Access Time (max) = 100ns
TMS4464-12NL Texas Instruments , Access Time (max) = 120ns
TMS4464-10NL Texas Instruments , Access Time (max) = 100ns
M5M4464-10, Access Time (max) = 100ns
 
Success!

I don't want to count my chickens too early but i replaced all the DRAM and SDRAM sockets.
Also replaced SDRAM U13, 14, 26 and 27 chips.
The last load of dram received was clearly old and had been desolder so i didn't have a great deal of confidence in it...
NOS stuff in new sockets appears to have done the job.

thanks for all the help.

Incase anyone else is looking for dram, there's quite a few options for replacements. i ended up with hyundai chips.

Lexicon Dram that should work, Access time should be 120ns or under.

D41464C-10 (uPD41464C-10) NEC Electronics , Access Time (max) = 100ns
P21464-10 Intel , Access Time (max) = 100ns
HY53C464LS-10 Hyundai Semiconductor , Access Time (max) = 100ns
TMS4464-12NL Texas Instruments , Access Time (max) = 120ns
TMS4464-10NL Texas Instruments , Access Time (max) = 100ns
M5M4464-10, Access Time (max) = 100ns
Hi.
I have the same problem. Random nintendo noise on machine B.
Did you replace all dram and sram on all boards? Or just the specific one?
 
I was following the thread because I had the same issue here.

I also succeeded on the repair. I just swapped 5 of the 10 DRAM chips of Machine A. I started from the ones of the channel that presented the issue with more volume.

I was seeing a peak in volume of the "glitch" on the left channel so I swapped the ones from the left channel at first. It solved the issue.

DRAMs are rare here in Europe...
 
I was following the thread because I had the same issue here.

I also succeeded on the repair. I just swapped 5 of the 10 DRAM chips of Machine A. I started from the ones of the channel that presented the issue with more volume.

I was seeing a peak in volume of the "glitch" on the left channel so I swapped the ones from the left channel at first. It solved the issue.

DRAMs are rare here in Europe...
Thanks for the reply. Did you find any in Europe? Right now eBay seems like the only option. And how did you figure out you only needed to swap out 5?
 
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