| NH7RO |
| 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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| mrfeedback |
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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| NH7RO |
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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| mrfeedback |
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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| NH7RO |
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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| NH7RO |
| 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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| mrfeedback |
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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| mrfeedback |
| Hi Jeff, I reduced the file size and posted it for you. ;) |
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| mrfeedback |
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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| NH7RO |
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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| mrfeedback |
Hi Jeff,
Low ESR means low Effective Series Resistance.
RB means vertically mounted electros with both leads out one end.
Eric. |
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| NH7RO |
Bingo! Eric, that 100uF LF rolloff cap in the right channel was the culprit. I replaced it with a Nichicon 35v electro and now the amp is back to normal--great bass in both channels. I also cleaned the boards well and got a lot of flux off!
Now just have to replace those fried resistors in my other 1150 and then I'll be ready to biamp my speakers in fine style.
Thanks ever so much for your kind assistance. I'll go ahead and recap both amps with the Hitanos in due course (probably from your source in Sydney as they don't seem available here in the states).
Cheers! Jeff |
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| Brett |
Eric,
Do you have a schem for the 6000B, and could I have a copy if you do please?
Cheers |
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| mrfeedback |
| quote: | | Do you have a schem for the 6000B, and could I have a copy if you do please? |
Nah, sorry.
I always end up fixing amps like these flying blind (that means no schematic, and not drunk). ;)
I think I do have a schematic on paper somewhere, but only the Lord knows which box.
If I find it oneday, I will think of you. :goodbad:
From memory, there is not much to them - input diff pair with current source transistor, and driver stage with transistor current source - 6 small signal transistors plus outputs I think.
These are still very well regarded amongst PA guys, and would make a limitless home power amp - the 8000b would be even more fun.
The 6002 (or 6200?) is rated down to 2ohms, at full power all day long.
I have been in contact with Duncan Perreaux previously - I might drop him a line.
For physical construction and sensible layout, a whole heap of designers ought to take a leaf out of this series design books.
Eric. |
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| mrfeedback |
Jeff, Glad to be of help.
Cheers, Eric.
PS - You need to change that same cap both channels - very important for channel matching. |
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| ShiFtY |
What are the 8000 and 9000 models like? I have heard it is possible to get ~900WPC out of these!! :bigeyes:
Are they good sonically, or are they mainly meant for PA applications?
Also are the output devices still around (or similar ones available?!) Could you just use less than 8 per channel if you didn't need that much power?
Thanks for the 20 questions, I know someone who might have some parts for one... Gives me an interesting idea for a new project :)
Thanks |
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| mrfeedback |
Sonically they are very good indeed, both home and PA.
The power output that they are capable of makes them essentially limitless for any domestic application.
Less output transistors would be fine for lesser power requirements - if anything these were overbuilt to ensure reliability in PA applications with low impedence loads, and would do it all day long.
10N20 and 10P20 are modern replacements for the original Hitachi Mosfet output transistors.
Do you have schematics ?.
Eric. |
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| Brett |
Hi Eric,
Thanks anyway. My 6000B is working fine and only needs a slight cosmetic cleanup; mounting bolt marks and a bit of corrosion on the fan guards. It spent it's whole working life doing <i>occaisional</i> foldback monitor duties in a small club, so it had an easy time, and will have an easier time now powering my horn subs (100dB/W).
I wanted the schem to make sure everything was up to spec (voltages correct etc). The signal caps will be replaced just to ensure reliabilty. It's never been touched, all the soldering is original.
It's an OK sounding amp, not great, but very nicely made and laid out. I'd never run it full range on my horns, but if I had low-eff squeezeboxes my opinion might be different. |
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| mrfeedback |
Hi Brett,
Open it up now and clean (isopropyl) all flux and any fog juice off the boards before it goes SPLATT. :bigeyes:
On the boards are two traces adjacent to each other that carry + & - 100V respectively, and any smeg here can cause them to exit bigtime.
Old fog juice and dust has been the demise of most of these that have gone expensively splatt - you have been clearly warned.
I also automattically just blanket resolder these boards too, and clean them again - a bit of laquer over the problem tracks is advisable also.
Take a closer look at earthing arrangements, and better pcb electros and you should be able to make it sing more nicely.
Eric. |
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| Brett |
Thanks for the tips Eric. At the moment it's sitting in my workshop awaiting the subs being finished, so I have plenty of time to go over it before it's in service. I've had the top off it and it looks clean, but I'll do as you suggest before I play it again.
Cheers |
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| mrfeedback |
Yes, from what I have seen, you are wise to follow up on this before it gets expensive - maybe change the trimpots too.
Also the internal audio cable could stand upgrading imo.
With one of these for subs you ought be be able to break your walls down, and those neighbours will be wishing that they were time transported. ;)
Eric. |
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| Brett |
| quote: | Originally posted by mrfeedback
Yes, from what I have seen, you are wise to follow up on this before it gets expensive - maybe change the trimpots too.
Also the internal audio cable could stand upgrading imo. |
I'm reluctant to change the trimmers unless I know what the voltages at that part of the circuit <i>should</i> be. I know I can measure it beforehand, but I don't know what's there now is correct.
| quote: | | With one of these for subs you ought be be able to break your walls down, and those neighbours will be wishing that they were time transported. |
Could that be one of the reasons they're moving? When the real estate agent rings and says they're bringing someone to look at the place, she comes over and asks me not to play the system for a little while. |
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| ShiFtY |
Cheers for the info.
Unfortunately don't have a schematic or any other info yet... Watch this space though. If I get one I'll let u know :) |
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| mrfeedback |
| quote: | | I'm reluctant to change the trimmers unless I know what the voltages at that part of the circuit should be. I know I can measure it beforehand, but I don't know what's there now is correct. |
What a big wuss. :nod:
One is DC offset - easy to work out which one by inspection, and the other will be 'you guessed it' BIAS current adjustment.
1) - Carefully mark all trimpots.
2) - Put an ammeter across one of the (say positive) DC fuseholders (both positive fuseholders if you have 2 ammeters) and WRITE the readings after achieving thermal equilibrium.
3) - Measure the DC offsets with inputs shorted and no loads.
4) - Carefully tweak the bias pots and note which direction causes diminishing of bias current, and mark the board accordingly.
5) - Shut the thing down, and when the supplies have decayed, replace the trimpots OR twiddle them back and forth to clear any noisey contacts.
6) - Reset the DC pots to the markings, and set the BIAS current trimpots to the minimum bias setting position.
7) - Bring the bias current back up to the previously measured values in stages, allowing time to reach thermal stability each step.
8) - Do steps 1 through 7 for the other channel.
In my experience trimpots are not always reliable and can go noisey.
I never let an amp out without changing them, or at least rotating them 20 times, and optional contact oil treatment.
'Select on test' bias setting fixed resistors can be tedious to get right, but are worth the effort long-term.
Do this treatment and my earlier advice, and it'll never let you down.
Cheers, Eric.
PS - Brett, I hope you don't mind me explaining this to you in such detail, but I think you told me that you were once a Broadcast Technician, and not a R&R Technician. :D |
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| Audiofanatic |
Hi Eric,
Does this means that the P200 Main Amp has the same problems?
To bad, the Perreaux P200 is gone, but I'll try to get it back so I can change the cap's and the internal cables.
What an eye opener! Thanks to you all.
Audiofanatic ;) |
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| mrfeedback |
Not sure, because I have not worked on a P200.
The above procedures I perform on all old high power (and low power) amplifiers that come over my repairs bench, and that way when I send them out I know that they are working at their optimum, and they should be completely reliable, and touch wood so far, I NEVER get the same amp back.
I repair high power amps for band PA systems usage, and my customers are happy to pay extra for a complete repair - an amp going down mid-show is not good for my customers.
I insist on this approach on old amplifiers because I do not want them coming back under workshop warranty with expensive blown outputs, and this method works for me and the customers.
I also find that a newly resoldered amp sounds much better too.
Eric. |
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| Tall Shadow |
| quote: | Originally posted by NH7RO
Bingo! Eric, that 100uF LF rolloff cap in the right channel was the culprit. I replaced it with a Nichicon 35v electro and now the amp is back to normal--great bass in both channels. I also cleaned the boards well and got a lot of flux off!
Cheers! Jeff |
Hello!,
Just a large word of warning about the use of Nichicon caps. I work for one of the largest suppliers of automotive electronics in the USA. We have found these caps to be VERY likely to leak on to Your PCBs. I have found that, in My experience here and In My Own business, that ANY Nichicon caps are better off being replaced.
Respectfully,
Tall Shadow |
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| mrfeedback |
Good point.
Yes I find plenty of Nichicons in various gear and find them to be unreliable too.
Eric. |
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| Brett |
| quote: | Originally posted by mrfeedback
PS - Brett, I hope you don't mind me explaining this to you in such detail, but I think you told me that you were once a Broadcast Technician, and not a R&R Technician. :D |
Thanks Eric, but that's similar to what I would have done anyway for a pot replacement. Your not entirely correct on one point: I've done plenty of PA amps before, and always used the approved and recommended technique. All an R&R tech need to know is, hose out the beer, dry it off, hit it twice with a large rubber mallet for luck, and send it back out. :) But your method only returns it to where it is now after pot replacement, and doesn't address my original point of wanting to know what it should be as per factory specs.
And y'see, this is <i>my</i> amp, and it's powering <i>my</i> expensive speakers, so I'm a tad fussier. A schematic will turn up. |
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| NH7RO |
| quote: | Originally posted by Tall Shadow
Hello!,
Just a large word of warning about the use of Nichicon caps. I work for one of the largest suppliers of automotive electronics in the USA. We have found these caps to be VERY likely to leak on to Your PCBs. I have found that, in My experience here and In My Own business, that ANY Nichicon caps are better off being replaced.
Respectfully,
Tall Shadow |
Thanks guys for your Nichicon alert--it was all I could find locally out here on this rock (Hawaii) for a temporary tryout. I still plan to round up some Hitano EXRs and replace ALL the electros but will have to send off to Australia to do so. Anyone here know of any USA source for Hitanos? My thanks again! Jeff |
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| mrfeedback |
| quote: | | All an R&R tech need to know is, hose out the beer, dry it off, hit it twice with a large rubber mallet for luck, and send it back out. |
You forgot the fog-juice and the roaches.
I know that PA amps will withstand a persuasive mallet hit, but I don't dare send them back out half done - if they fail mid show I get my butt kicked, plus I have to fork out for new parts.
I prefer to do it properly in the first case.
By the sounds of it you have worked with too many shonky R&R technicians.
I have worked with a few shonky Broadcast Techs too - if they don't have a circuit manual they can't work it out, or if they can they'll take all day - those kinda guys are no use to me in my repair business. - Sheltered Workshop techs we call them. :nod:| quote: | | But your method only returns it to where it is now after pot replacement, and doesn't address my original point of wanting to know what it should be as per factory specs. |
Hi Brett,
I mean, when I renovate any big amps I change pcb elecros, maybe trimpots, whatever is blown, blanket resolder, clean the boards and then cal bias and dc offset - I reckon that is a pretty complete job, and they don't come back under workshop warranty.
If I do not have bias current specs, I measure bias both channels and make an informed decision on where to set both channels.
Dc offset is of course 0V wrt to - speaker terminal.
I usually have a listen whilst adjusting bias within sensible range, and listen if there is any sonic difference - usually not much.
The preferred method would be to run thd and imd measurements at a range of bias currents.
For big amps I tend to slightly underbias them in the interests of reliability - at some outdoor summer shows (40*C days) the amp racks can get too hot to keep your hand on.
For home listening, finely adjusting the bias current is practical.
Eric. |
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| Brett |
Eric,
I was taking the ****. Sheesh. |
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| mrfeedback |
| Me too !. :nod: |
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| wolfman |
Hi there ! I just picked up a 1150-b and it has significant distortion in one channel.. any ideas ? Would that be the output transisitors?
any help would be much appreciated.
Bernard |
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