Can anyone fix a Lexicon RV-8 for audiodon?

Thanks Erik! Good catch. I'll order one and a spare.

Update - I just ordered two switching supplies. A spare isn't a bad thing to have since one has failed in each of our units. Those things must have run hot.

Lexicon was near me in Bedford, MA when the RV-8 was developed. They're long gone from here as part of the Harman buyout. I went by their old address to be sure. Gonzo. But maybe some of the people who worked on the RV-8 are around in Lexicon or elsewhere and might have some insight. I'm going to do some digging. I still believe that this must be a known problem. Who knows what it is? I hope to find someone who lived through it at Lexicon.

I have a 4 channel scope. After I get the new power supply in, I'm going to fire up the unit and start looking at what the CPU bus and data lines are doing after a reset. A stuck data or address line will kill the system. If the CPU won't keep running, I may add an external circuit using an Arduino to keep blipping the CPU Reset/ low so I can successively probe the I/O lines after reset to see if any of them look stuck. It's worth a shot...
 
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Sure thing. It turns out that two of the principals at Lexicon are local to me. I emailed one yesterday and will email the other one today. I hope they can send me to someone who is or was at Lexicon on the Tech side.
 
No news. I emailed the two former Lexicon people but heard nothing back. I'll try calling them.

I did receive the two switching power supplies I ordered today. I may have some time to look at the Lexicon the week after next but no promises.
 
Thanks. If it can't come back to life as an AVR, there are seven 140WPC Crown amp channels and power supply in the box that might have a second career as a fancy power amp system. I hope it doesn't come to that but who knows...
 
Dan I so wish I had the ability to fix that for Don. I've found a good tech recently but he tells me he'll work on just about anything except av gear. The Crown would more than fill his needs I'm thinking?
 
No news. I emailed the two former Lexicon people but heard nothing back. I'll try calling them.

I did receive the two switching power supplies I ordered today. I may have some time to look at the Lexicon the week after next but no promises.
Cool!
 
Thanks. If it can't come back to life as an AVR, there are seven 140WPC Crown amp channels and power supply in the box that might have a second career as a fancy power amp system. I hope it doesn't come to that but who knows...
I hope that I will not have to concede to that but...thanks for the idea.
 
Minor update but no good news: I decided to swap in one of the new switching supplies I just received. I was pretty sure that I had ruled out the low +5V supply problem as the major issue since I had subbed in an external 5V supply and the symptoms stayed the same.

But hope springs eternal so I pulled out the bad supply, put in the new one, powered the unit up and...

No change. Ah well. I'm going to put it away until I have time to go through it in more detail, checking sub supply voltages and seeing what the CPU signal lines are doing.

No free lunch. :no:
 
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Yes, when I swapped my power supply out, it did not resolve the issue as well. All of the voltages check out on the main board as well, so I am hopeful that you will find something with the scope. Thx
 
And now the bad news. I bought the power supplies from Pyramid Audio in Austin. I looked them up last night and found that they are a Lexicon service center. So I called today and spoke to Chris in Engineering.

He said that the +5V on the switching supply in the RV-8 typically failed and went high. That damaged things on all of the digital boards including the Crown amp boards. When the RV-8s were under warranty, repair was a $2000 project that required multiple board replacements. He says it isn't worth doing now and I think the replacement boards are no longer available. I asked if the amp boards could be salvaged and he said they'd be damaged too.

Bottom line - A dead RV-8 is probably gone for good. Figuring out what is damaged and replacing a bunch of SMD parts isn't something that I have the time or expertise to do. Not a good status report, I realize, but that seems to be the truth.
 
Thanks for the update. Let me know if I can take your unit off of your hands for board swaps. With the kids off to college, I may make a hobby of fixing this unit! Does anyone know how I can get my hands on a scope for a few days? any recommendations?
Thanks,
Erik
 
Erik. I'll ask Don what he wants to do. Since it's essentially worthless as is, trying to sell it is pointless. However, I still think I might take a serious crack at it but probably not for a while. At the very least, I might try the "keep blipping the reset and see what does and doesn't show any life" trick.
 
I secured a scope for a week! My finding is that the clock input pin 74 on the main processor is 6.25mhz but only at 1.76 volts. This seems low to me since it is a 5v chip but I wanted to see what others thought. Thoughts? I cannot find a clear acceptable range in the chip documents.
 
I am pretty confident that I have found the issue. U44 is not sending out the divide by 2 of the clock to the CPU at an appropriate voltage. It is a GAL16V8R-15 which is a programmable chip with 360-15249 v1.00 software. It is a 20 pin LCC package. Any advice on finding a replacement? and how to program it?
 
Hi Erik. I'm glad that you're finding some issues. My conversation with Chris at Pyramid Audio the other day lead me to believe that multiple chips on multiple boards typically get blown out when the 5V PS fails high. If so, there could be more trouble in other places. I should have asked him if anyone has ever repaired the main board and what parts failed on it.

I didn't plan to work on the Lexicon next week since I have other things to do. If I get a chance, I'll look at the same signals you checked out.

FWIW, Chris at Pyramid replaces the original PS with a fan cooled unit. Or maybe he adds a fan to cool the PowDec PS. Clearly something needs to be changed to prevent the problem from reoccurring if the unit is brought back to life.

Pyramid is selling a used RV-8 for $1200. See the notes about the upgrades they did.
http://www.pyramid-audio.com/used.html
 
Well, I have figured out how to clone the chip using a TOP3000 programmer but I need a good chip to do so. Does any know if the +52010542 that is listed on the chip in the schematic has any meaning?
 
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