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Old 28th January 2008, 09:16 PM   #11
RCruz is offline RCruz  Switzerland
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Please note that my amps are POA 6600 A with a optical chip in the bias circuit.
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Old 29th January 2008, 07:15 AM   #12
bekim is offline bekim  Albania
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Ok,

I had similar problem with many equipment, including denon power amps. Seems that, you have many "bad solder" to remove and put new one across the whole pcb.
What you have to do is:

-remove all 2sa1492/2sc3856 from pcb,
-check resistor value in each transistor placement, i.e. in each npn transistor should be the same value, might be any connection broken....
-instead of posistor you put 100ohm (or 220ohm) resistor,
-make sure all transistors are ok, be sure to check each of them,
-replace trimmer pots, in both pcb, and approximately slide the new pots to the same value like old ones,
-existing zeners are 5.1volts/400mW, put new ones 5.1/500mW you can find philips bzx5c1,
-replace all biasing diodes, those standard ones 1s2076, with 1n4148 usualy are better than those on your amp,
-check for 8pin ic's, M5238 & NJM2068, might be trouble.. you can replace temprorary with ne5532 or equivalent,
.....

As I can see from problem you have with this amp, I think that, bad solder causes this blowing of all trannies.. It happen before to me as well. Is very important to have very good solder and clean iron in order to make good joint, is prefered to remove the older solder and put new one.

Ricardo, big power amps run pretty hot and, ,ost of the fault is done from bad soldering.

Make sure to check all parts, you might missed some bad part, or similar causing problem maker. Is very important if you change electrolytes on amplifier pcb, in case there are not many, there 10uF/50v replace with 10uF/63v and check bipolars as well, 1uf/100v.
check transistor value of TR601 RSN1205 might be problem..
R553 & R554 1kohm resistors might loose thier values, or might have bad solder.
When you are sure about all this and you want to check your amp, usualy don't connect all trannies on output, instead you can put just one pair - one 2sa1492 and one 2sc3856, and to check is it working or not. Or better, if you have any other cheaper pnp/npn pair put there instead of original ones, just for testing.
And, most important is to set biasing according to service manual.
If you don't have service manual I will send it to you.

Let me know do you have problem only with one or both amps..?

bekim
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Old 29th January 2008, 07:38 PM   #13
RCruz is offline RCruz  Switzerland
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Quote:
Originally posted by bekim


-remove all 2sa1492/2sc3856 from pcb, (Done)

-replace trimmer pots, in both pcb, and approximately slide the new pots to the same value like old ones
Can not find replacements in farnell can you help ?
Quote:
Originally posted by bekim

-replace all biasing diodes, those standard ones 1s2076, with 1n4148 usualy are better than those on your amp,
Should I replace all 1s2076 in the schematics or just the bias ones ? Can you please point them on the schematic ?
Quote:
Originally posted by bekim

-check for 8pin ic's, M5238 & NJM2068, might be trouble.. you can replace temprorary with ne5532 or equivalent,
Do you mean replacing IC601, IC602 and IC401 (NJM2068AD) all by the same type of opamp (ne5532) ?
?
Quote:
Originally posted by bekim

check transistor value of TR601 RSN1205 might be problem..
Also can not find TR601 on the pcb can you point it out for me ?

I have two amps and one is working perfectly.

I just received the HZ5C1 from UK and have some output TR that I believe to be fake ones.... Can I use these for testing ?

As I can not find true 2SA1492 and 2SC3856 anywhere, can I use 2SA1294/2SC3263 instead ?

Thank you very much Bekin

Ricardo
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Old 30th January 2008, 07:18 AM   #14
bekim is offline bekim  Albania
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Hi Ricardo,

regarding helping you to find original 2sa1492/2sc3856 I don't believe that I can help somehow. I live in Kosova and, all parts which I order are from asia - somewhere, don't know the origin precisely.

biasing diodes you have to replace only, not all. You point on those near zener diodes like, D511, D514, DS515, D516, D517, D518, D519, D520 these are 1S2076, and you can change them with 1n4148. Diodes D512 & D513 are zener HZ5C1 you can replace with BZX5V1 if you cannot find original ones.

OP's IC601 & IC602 you can change with NE5532, or NJM2068AD in both places, I did this on one broken amp like yours until I fix it then, I put new original ones. But, if you're sure that, those IC's are ok, don't change them. Eventhough, you can replace both IC's with M5238 when you finish fixing your amp.

TR601 is placed near R608 and C604 on your power amp board. Desolder it and check does it show short circuit, and if is ok put it back.

You can use 2SA1294/2SC3263 but, remember to not destroy all transistors on output, put just one pair on power amp board; example TR513 & TR514. You can always put any other cheaper trans there even fakes, just to see does it work. just make sure that bipolars you will use for testinga re not darlingtones.


replace all these electrolytes - is highly recommended:
C501, C507, C508, C523, C547, C601, C602 - 10uF/50V, you can replace with 10uf/63V;
C604 10uF/16V;
C516, C517 - bipolars 1uF/100V;
C524 22uF/100V;
C543 & C544 10uF/100V bipolars.

I don't know how old this amp is, therefore all these electrolytes are better to be replaced. condensers are pretty annoying and difficult to be sure that old ones are ok, regardless how much time you spent on measuring them.



bekim
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Old 30th January 2008, 09:53 AM   #15
RCruz is offline RCruz  Switzerland
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Hi Bekin

I will do as you indicate during this weekend.

I will report after that.

Please inform if I can use 2SA1294/2SC3263 to replace original ones as I need to order them now.

I already have some 2sa1492/2sc3856 but I believe they are fake ones because I bought them very cheap and they look like some fakes I have seen in the internet.

Thank You for your help.

Ricardo
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Old 30th January 2008, 01:01 PM   #16
bekim is offline bekim  Albania
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Yes Ricardo, you can use 2SA1294/2SC3263 for your amp.

Technicaly these are best matching transistors if you cannot find original ones.
I am just wondering, how much these trans. costs at your place, price in euros..? Price per piece...
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Old 30th January 2008, 03:35 PM   #17
RCruz is offline RCruz  Switzerland
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Farnell 1192129
ALLEGRO SANKEN 2SC3263 TRANSISTOR, NPN TO-3P 4,85

Farnell 1192130
ALLEGRO SANKEN 2SA1294 TRANSISTOR, PNP TO-3P 4,57

Farnell collects + 9 for every mail package.

Can you get originals for less ?

Regards

Ricardo
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Old 31st January 2008, 09:04 AM   #18
RCruz is offline RCruz  Switzerland
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Hi Bekin

Last night, after replacing the bias diodes with the correct ones, I installed two output TR and fired the amp.

It seems to be ok because it did not get hot and nothing burned.

Nevertheless I am still measuring differences in the base voltages of TR509 (1.55v) and TR510 (-1.69v).

Can I load the output of the amp and input some signal ?

Also I am reading the following voltages in TR551:
Base -1.16v (should be -1.1v)
Colector 1.74v (should be 1.75v)
Emitter -1.88v ( should be -1.7V)

This last reading is very troubling because the emitter should have lower voltage than the colector and I believe this is the source of the differences I am reading in th driver stage.

Can you please suggest a corrective action ?

Best Regards

Ricardo
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Old 1st February 2008, 07:00 AM   #19
bekim is offline bekim  Albania
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that's good.

Ok, if isn't blowing anything, check sorrunding electrolytes of TR551 and other parts, because should be very near to data given on service manual.
Regarding TR509 & 510, that's normal, isn't very high difference.
Try to align bias according service manual and when you're sure about it, but REALY sure, then connect 8ohm speaker and turn speakers on, and without signal chack after 20minutes does the output trannies are getting little hot, as well check for voltage in base of output trannies. If doesn't blow, connect signal, but don't play it loud and see how it performs.... after that you can put additional two more trannies, and do the bias aligning and so on....

BUT, prior to this, did you check for "bad" soldering?
did you measure electrolytes or change them...?
did you check biasing diodes and zeners...?

try to check these parts, and be sure are ok.

bekim
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Old 1st February 2008, 08:53 AM   #20
RCruz is offline RCruz  Switzerland
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Hi Bekin

I did check for bad solder and fixed most of the visible points.

I am having trouble checking transistor value of TR601 RSN1205 ... can you explain how can I check it ?

I can not find this transistor in Portugal.... can you suggest a internet seller for me ?

I already ordered the el capacitors (10uF 63V) and (22uF 100V).

I will replace them this weekend.

Unfortunatelly I can not find any bipolars in Europe providers.... can you help ?

Best Regards

Ricardo
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