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Old 1st February 2008, 10:30 AM   #21
bekim is offline bekim  Albania
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TR601 RSN1205 - just check if it has any short - circuit on it, otherwise should be good..

Ricardo - I don't know how to help you with finding parts, I have very different system here, just I order parts to some specific traders and they will find them for me..
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Old 3rd February 2008, 12:13 PM   #22
RCruz is offline RCruz  Switzerland
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Hi Bekin

I replaced all EL caps as you suggested and also TR551.

I reinstalled the board and now the amp does not come out of protection (front panel led protector keeps blinking).

After a wile, resistors R553 and R554 blew in smoke .

I replaced these with 1/2w 1kohm but the amp does not come out of protection and I can measure +- 81v on the R553 554 resistors.!!

Also I read +-80v on the base of TR509 / TR510.

What should be the cause of this problem ?

Can the output transistors be blown again ? (measuring resistance between colector and emitter of TR517 / 518 I get almost 0ohm, when the amp is not on).

Are the outputs shorted ?

I am afraid to do much more before you comment on the actual situation.

Best regards

Ricardo
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Old 4th February 2008, 08:03 AM   #23
bekim is offline bekim  Albania
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Ricardo,

"After a wile, resistors R553 and R554 blew in smoke"

--did you check drivers TR509 & TR510..?


"Can the output transistors be blown again ? (measuring resistance between colector and emitter of TR517 / 518 I get almost 0ohm, when the amp is not on)."

--YES!!


Listen, I don't want to offend you in any matter, but can you find any one who is fixing amps and have checked amp together. Because, if you did all these thing in your amp and still is blowing parts, something is wrong here.

bekim
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Old 4th February 2008, 09:41 AM   #24
RCruz is offline RCruz  Switzerland
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Hi bekin

I do not know of anyone able to fix these amps in my Country.

That is why I tryed to have a go myself.

The problem is that this amp has been fixed several times by several different people and I can not know what have been done before.

I find many points where solder is not good and some other points where the copper lines in the pcb are loose or have been replaced by wires.

This PCB is very problematic.

Do you know if I can find another main board PCB and where ?

I am very frustated because I spent a lot of money buying new parts that I can not install right now.

Thank you for your support.

Regards

Ricardo
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Old 5th February 2008, 07:45 AM   #25
bekim is offline bekim  Albania
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Quote:
Originally posted by RCruz


This PCB is very problematic.

Do you know if I can find another main board PCB and where ?


Man,

I know your pain, if this is the case that, pcb is broken, you have carefuly and a lot of patiente to work with this pcb. yo have to be more than 100% sure to connect all wires properly where the leads are cut off. Use wire in order to connect all leads and be careful when you do this just to not connect something else.
I didn't know in begining that, you have this problem. This requires a lot of attention.

If you can send me a picture of back of pcb will be nice. Send me more pictures, not just one.
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Old 14th February 2008, 07:49 AM   #26
bekim is offline bekim  Albania
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Hi Ricardo,

any good news about your amp..? Did you manage to fix it?

bekim
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Old 14th February 2008, 11:39 AM   #27
RCruz is offline RCruz  Switzerland
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Quote:
Originally posted by bekim
Hi Ricardo,

any good news about your amp..? Did you manage to fix it?

No luck.... I believe I have a damaged TR601 (TOSHIBA RN1205)and can not find a suitable replacement in Europe.... Can you suggest an alternative ?

Regards

Ricardo
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Old 14th February 2008, 12:02 PM   #28
poynton is offline poynton  United Kingdom
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Hi.

Do you have this :-


http://pdf1.alldatasheet.com/datashe...BA/RN1205.html

They look like standard NPN transistors with the built-in resistors.
I would guess that you could "make" your own on a bit of vero-board.



Andy
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Old 14th February 2008, 04:29 PM   #29
bekim is offline bekim  Albania
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Quote:
Originally posted by RCruz


No luck.... I believe I have a damaged TR601 (TOSHIBA RN1205)

Does it shows any short circuit when you measure transistor.. i.e. does it "beeps" when you try to check terminals of Base, Collector & Emitter...? You have to be SURe that this trans is dead..

You can "made" other transistor with 2SC2240 but you have to add additional resistors one is 2.2kohm and another one is 47kohm, please search for RN1205 in this site and download pdf so you can see how to connect these resistors.

http://www.datasheetcatalog.com/

You can use many transistors equivalent to original as, 2SC2240, 2SC1815....etc...etc

bekim
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Old 14th February 2008, 07:27 PM   #30
RCruz is offline RCruz  Switzerland
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Thank you Bekin

I believe the transistor is not shorted but the resistor values are very different from the one in the working amp.

Note that I am measuring the two amps to compare, with everything in place.

Before the recently trannies blew I measured the following differences on TR601:

Bad Amp B 15.2mv C 137.4mv E 0v
Good Amp B 0.5mv C 13.9mv E 0v

Another question...:

Can the optocoupler be dead ? (When the output trannies blew, I measured -80v on pin 3 of IC501... so it can be affected)

I bought some new ones but they seem to have different specs:

The original is TLP521-1 (BL)

I have got the replacements:
TLP521-1(A,F,T)
TLP521-1(Y)
TLP521-1(GB)

Can I use any of those ? (The difference between them and the original part seems to be related only with the precision of the Current Transfer Ratio (%):
Original - Min 200% Max 600%
TLP521-1(GB) - Min 100% Max 600%

I believe the problem is related with the bias circuit but can not identify the reason.

Can you please send me a schematic with comments regarding the several sections ?

How can I look for the reason the values in R553 and R554 are not simmetrical ?

And the grey whire should be 0v and I always have -.07v...why??

When i adjust VR501 I can modify the voltages in R553 and R554 at the same time, so the raltive difference is not altered.

When I adjust VR502 the only difference is on pin 4 of IC501 that can vary in only .05v.

Is this normal ?

Best Regards

Ricardo
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