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TheLastByte 15th July 2015 04:35 AM

Lexicon PCM-70 FET - DEAD Output problem
 
1 Attachment(s)
ATTENTION:
LEXICON PCM-70 USERS.

If you own a Lexicon PCM-70 you will want to take Notice:
Lexicon PCM-70 Static FET problem: 15/7/2015.

After having just written this Post and being timed out from a GS forum, I shall rewrite it as it's an issue that has affected Lexicon PCM-70 owners in the past, and recently did again. Unfortunately now Lexicon has seen the days of being at the pinnacle of Reverb and Effects design gone! More so there are many Service Bulletins and Engineering ECO files coming to notice. Certainly all Manufactures have problems, from TC Electronic, Roland, Yamaha, Korg, Eventide, and all provide Software Updates and Fixes though Lexicon seem to take the Biscuit Here! Most other OEM's provide full disclosure and/or give general fixes to the public, for some strange reason Lexicon's Service ECO's have been marked for Technicians only and not for publication, and more are surfacing!

So you have you're Studio and Sting, or Springsteen, or even Gilbert O'Sullivan is sitting next to you as you are mixing his next come back Album be it in the Box or on a Console, maybe you keep a bunch of Software Plug In's, though for some reason feel that when mixing, your Eventide H3000, Bricasti or Quantec and Lexicon PCM-70 apart from your Korg and Roland Delays come in handy to bring out that extra wide Reverb you like to use. Today sitting next to Gilbert O' Sullivan and Re-Mixing "Alone Again Naturally" as Phil Reeves has booked you for an Xmas comeback album you need to get a move on, those Drum Sub Groups need a "touch more Compression& Reverb and the Lexicon PCM-70 Tiled Room Preset would work perfectly".

ITB or Out, you reach into your Rack and Get the output cables from the Lexicon PCM-70. Then…..You get the Input Cable in though it's touched the Outputs or you're using a Patch Bay and you accidentally take the Output from the PCM-70 and with the Static on the Rug on your Wooden floor accidentally touch the Output to Output of the PCM-70, though it's Ok... no problem, you didn't push the cable into the Patch Bay, though Touching Thru the Patch Bay created enough Static, yes, it was enough worse it blew the PCM-70 Relay output FET!

Suddenly, the Lexicon PCM-70 you've been using for the Last 15 Years is seeing Input Signal, though there is No Output Signal, you re-check your cabling, and it's all good, though still, you dial in TILED ROOM and nothing. No Signal! No output Signal….Why? Simple, that tiny amount of Static was enough to blow the FET on the Lexicon Outputs Relay of the PCM-70 and It's a known Lexicon PCM-70 fault going back to PCM-60's. If the cable touches the Input or Output with Static you can blow the output Relay FET. Lexicon State from Serial Number PCM-70 Units made prior to this serial number #70-1807 have this fault, and it has not been taken care of, recently I found a friend who's units FET blew by this exact scenario. So a word of caution. Keep you're PCM-70 Output Cables well away from any PCM-70 Inputs and Static. Below is a PDF File. If you do DIY you can install this FIX. If you have this problem any tech should be able to fix it.

Also, while on the subject, many PCM-70 Screens are becoming unreadable due to the buildup of condensation over the years caused by humidity, so the PCM-70 screen is cloudy? What to do? Well it's a simple Fix. Grab a Can of Lubricant from Caig, and a Hex or Allen Key. Simply Hold the Front Panel, Pull of the Knobs, and the Front Panel of the Lexicon PCM-70 will come off if you undo the Hex Key Bolts. Once you have the Screen off, use some very, very mild detergent, wash with distilled water, gently wipe away any humidity marks, and the screen will be 100% back to original condition. This happens when units are moved from Hot zones to cool zones, try to keep a small humidifier going in your Studio room. If you're Lexicon PCM-70 Outputs have gone silent, please read the PDF at the bottom of page and call your closest Tech.

Regards
TheLastByte


https://www.gearslutz.com/board/atta...1&d=1436931105

Elmbeatz 15th July 2015 10:35 AM

Thanks a lot TLB!

SaxnFlutman 29th September 2015 12:45 AM

Thanks so much! I've had this problem for quite some time, and no one had a clue as to what the problem was, much less fix it!

Oh, TLB, any idea where I can get the parts from? Are they generic, or do they have to be Lexicon made, and if so, would they even have them?

aramism 29th September 2015 04:48 AM

best lexicon service guy ever. beamish electronics in ohio....

has serviced tons of old lexicon gear from 42s, 70s, and 224x for me in the last few years. still around, still services all old lexicon stuff and a champ of a guy to boot. highly recommend.

TheLastByte 30th September 2015 01:51 AM

Hello PCM-70 Users, as to where to get this FET and it's part number, I'll try and upload the PCM-70 service manual for you, it's a simple fix, though also (For PCM-60 users) try to do the cut and jump procedure so it can not happen again!

As The Esteemed GW Bush Greatly said:

"Fool me once... erm....Fool on erm... yeah... you! Though...Fool me twice and erm, Fool on you, no, erm, yeah, erm....no? Ahhh, F*ck...where's an intern? How does it go again...?"
Lol......!

Regards
TheLastByte !

SaxnFlutman 7th October 2015 03:11 AM

Quote:

Originally Posted by TheLastByte (Post 11369584)
Hello PCM-70 Users, as to where to get this FET and it's part number, I'll try and upload the PCM-70 service manual for you, it's a simple fix, though also (For PCM-60 users) try to do the cut and jump procedure so it can not happen again!
Regards
TheLastByte !

I know the part number(s): 310-04289, J105/J108 and then it mentions it should be retrofitted with four diodes to prevent the FETs from blowing out. Although I'm not sure if anyone can do that, or would you have to be a real expert.

But I too, am dying to know if I really need the specific Lexicon parts, or if the FETs are more generic, and I can find it locally (Atlanta)... Thanks...

Oh, and what's the "Cut & Jump procedure"?

TheLastByte 8th October 2015 02:50 PM

Quote:

Originally Posted by SaxnFlutman (Post 11387545)
I know the part number(s): 310-04289, J105/J108 and then it mentions it should be retrofitted with four diodes to prevent the FETs from blowing out. Although I'm not sure if anyone can do that, or would you have to be a real expert.

But I too, am dying to know if I really need the specific Lexicon parts, or if the FETs are more generic, and I can find it locally (Atlanta)... Thanks...

Oh, and what's the "Cut & Jump procedure"?

Hello Saxn
Please see if your Lexicon PCM-70 PCB in your unit - If the PCB Board says Rev 1.0 and/or you've had problems - follow the procedure in the PDF File above, if you are not confident, ask a tech to do it, with the PDF Guide.....10 Minute Job, no more problems. Yes any FET that matches the Listed one will be fine! $40.00 Fix. Inc Parts!

PM if required!
Kind Regards
TheLastByte

"If you have a Lexicon PrimeTime M93 Original or Prime Time MK-II M95 or even a Super Prime Time-M97 as well as PCM-41/42 Units and PCM-Units from the 60 Onwards. I am Soon to embark on MEO Expansion of these Units, 7.63 Seconds (Older Prime Time Units) will be the Maximum Delay time with "Reverse Option" Added. Also Please understand other Extensions will be offered for Lexicon units by Qualified EE Technicians in a Group Buy. Please PM for Details to myself TheLastByte and I will reply to you!" - Please Allow 3 - 5 days reply as interest has been huge! - Thank You"