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Old 7th May 2003, 11:38 PM   #1
NH7RO is offline NH7RO  United States
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Default Recapping a Perreaux 1150B amp?

Anyone here ever recapped a Perreaux 1150B 100wpc amp? I have very low bass output in one channel and a number of small metal can caps w/ axial leads (polarized) appear to be leaking a dry waxy substance...Time for recapping? 1150B is 20+ years old and I imagine bad caps are the culprit. Does anyone know what kind of replacements I should use? Besides the old West German little cans, WIMAs and some banded,color-coded (poss ceramic?) caps are also used throughout the circuits. One last question: Should I try to also replace the two big 18000mfd power supply caps or wait until doing all the small ones first? All replies will be greatly appreciated! ---Jeff in Hawaii
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Old 8th May 2003, 07:29 PM   #2
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Default Just Do It.

Hi Jeff, I have plenty of experience with high power pro Perreaux amps - 6000B, 8000B etc.
At 20 years old, just replace all the caps regardless, excepting the 18,000 uF resevoir caps - these are maybe duff, but are very likely fine.
The other fault with Perreauxs in my experience is that the joints are soldered, and then the leads cut, and the flux is left on the board - this is all bad news for long term reliability.
My standard procedure is to clean the pcb's, replace all the caps, blanket resolder the pcbs, and then clean them again.
I have had very good sonic sucesses with these Hitano EXR low esr caps, and they are cheap.
Take care with bias current on initial start-up (use a variac) and you should have a brand new amp again.
Once this job is done correctly your amp should sound as good as it can, and it should never let you down.

Eric.
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Old 8th May 2003, 10:22 PM   #3
NH7RO is offline NH7RO  United States
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OK, Eric, thanks for your reply. I'll try the Hitanos for replacing all the 10-100uF electrolytics as you suggest. As for the smaller .1uF WIMAS I'll go with some sort of good quality polypropylenes.
Sorry if this is a bother but I still have a few more questions:

1) As for the four color-coded caps that look sort of like chiclets--yellow top, purple-orange-white-red bands in descending order--are these 473pF 92v if I figured correctly? If so, good quality silver mica or polyprops to replace these?

2) Anything special you use for cleaning the PCBs? Isopropyl alcohol & cotton swabs OK?

3) I dont have/have access to a Variac. Does the bias need to be reset or adjusted after recapping even if I'm careful to replace with exactly the same values? There are a couple of variable resistors per PCB side that appear factory-set, but I don't think I should touch them without proper knowledge & test gear.

Any further enlightenment before I order the caps will be tremendously appreciated! Thanks again,

Jeff
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Old 9th May 2003, 05:22 AM   #4
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Default Renovate It In Steps....

No bother, Jeff.
I would take things one step at a time.
I would do the blanket electros change/blanket resolder/pcb clean treatment first.
This will bring the amp to as good as factory and usually nicely better.

Try to stay with the same voltage rating and replace all the pcb mounted electros with the Hitanos, including coupling caps.
You may want to increase values of some electros too.
I find the these caps to sound good, clean and musical in all the applications that I have used them.

My next step would be to add RC networks across power supplies and windings, and get the power supply to sound decent, and live with that for a few days at least.

Once you have this reference, then go ahead and change polyesters to PP, also any ceramics to something better.

1) - Little square ceramics I think by your description.

2) - Newsagent art brush (long stem, flat white straight bristles, $1.00), Isopropyl alcohol (in a 200 mL squeeze bottle) and a toilet roll.
Wet the whole board, dissolve with the brush, dry the brush in the tissue and repeatedly wick up the dissolved flux/alcohol.

3) - Remove the fuse, and put a lamp across the fuse holder (40W or 60W then, 100W).
This will limit fault currents and allow you to run it up more safely.
ALWAYS, BUT ALWAYS check and set bias currents after any reworking.
You need a DVM - a $15.00 el-cheapo is good enough to set bias and DC offset (the two trimpots).
Use temporarily soldered in test point lead out wires for these fine adjustmets - ask if you don't understand these.

Use Multicore Savbit (60Pb, 38Sn, 2Cu) for good wetting/tinning and good sonics.
Treat all contacts, switches and controls.

Need any more info ? ..........just ask.

Eric.

Can you post photos ?.
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Old 9th May 2003, 10:18 PM   #5
NH7RO is offline NH7RO  United States
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Thanks, Eric, for the additional info and yes, I'll attach a photo of one PCB to help clarify things (right after this posting).
Coincidentally, I received a second 1150B yesterday afternoon that I bought on eBay last month (for biamping). I opened it up to compare parts and discovered four blown resistors and an almost-blown rail fuse... Nonetheless, I hooked it up to some cheap speakers and it still works. Actually sounds good, as if nothing was wrong. Maybe it was a protection circuit or bridging circuit that failed leaving the main circuits intact? I'll worry about this later and get back to our original subject now but must add that I did also discover the value of the color-coded "tooth-shaped" caps in item 1) in doing so-- they're .047 Wimas (probably uF unless pF indicated?) in this later serial # amp and the 10uF/100v German electros were replaced by 160V Marcon/Maxcons (?) (Hard to read very tiny brand name).

Item 2) No problem, can do.

3) OK, but how should I know what the bias current/voltage should be? Will I need to order a schematic/service manual from Perreaux? They want $50USD just for a schematic, if I recall correctly.
One last question: Any ideas on where to find the Hitanos in USA? Or elsewhere if no US distributor? So far, no luck trying to track a retail source down over here. My many thanks to you again Eric!
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Old 10th May 2003, 12:41 AM   #6
NH7RO is offline NH7RO  United States
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Eric, I tried to attach a jpeg 4 times to no avail. If you need to see it still, let me know and I'll try via direct email (97kb jpeg)
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Old 10th May 2003, 03:28 AM   #7
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Still waiting for the photo....
3) - I can send you prices and details to get the caps from WES .
They operate a very good mail order service, and always have stock of everything, and their prices are really good.

Eric.
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Old 11th May 2003, 12:32 PM   #8
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Hi Jeff, I reduced the file size and posted it for you.
Attached Images
File Type: jpg perreaux pcb r.jpg (20.0 KB, 658 views)
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Old 11th May 2003, 01:13 PM   #9
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Hi Jeff, the black electro is the LF rolloff cap I think.
If this cap is dry, then expect diminished bass output and lower sensitivity.
I do not know of any low ESR caps in the axial package, only RB types.
What are the values of all the electrolytics ?.
If you do some drilling you may be able to mount RB types.
I would replace the caps and blanket resolder the boards before any other mods, and see (hear) what you get.

Eric.
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Old 11th May 2003, 09:44 PM   #10
NH7RO is offline NH7RO  United States
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Thanks for posting the reduced jpeg, Eric. If you still need to see the complete boards I will send you more images but you might have solved my problem by possibly identifying the LF rolloff cap, a 100uF 25V Anodia CE 04W (One per side). I may just pick up a pair of whatever Radio Shack sells in that value and make a temporary fix to see if that's the root of the low bass output problem. Then I can replace the rest when I can round up the Hitanos (and new resistors for the other amp).
Sorry but I don't know what ESR or RB types mean. Could you enlighten me a bit further? Thanks, Jeff
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