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
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
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
"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
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
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
RCruz said:
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.
Hi.
Do you have this :-
http://pdf1.alldatasheet.com/datasheet-pdf/view/82026/TOSHIBA/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
Do you have this :-
http://pdf1.alldatasheet.com/datasheet-pdf/view/82026/TOSHIBA/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
RCruz said:
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
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
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
Hi bekinbekim said:
I have been measuring base emitter voltage drop in all transistors (not the outputs wich are not installed) and the values are all between 0.55 and 0.62v so everything looks fine.
In the case of TR601 i only read 2mv !!
Also in the case of TR602 where emitter base drop is only 35mv.
Can these be faulty ?
After some hard work replacing bad solder, I finally get some stability.
nevertheless, the values in the base of NPN trannies is 0.33v and -0.5v on PNP base.
I can not make these values to be simmetrical... can I install some trannies with these values on their bases ?
Best regards
Ricardo
Hi Ricardo
sorry for late response, I was celebrating Independence of Kosova..
regarding optocoupler, you can use any TLP521 regardless of last markings..
if your transistor TR601 shows very low value in your digital multimeter, i think you have to replace it or "made" it as I told you previously. But, try something else:
- put in pcb all parts except output trannies..
- as well, drivers put in your pcb..
- turn your amp ON and measure the values on TR601 and on base of output trannies - both pnp and npn.
If now will not burn anything, this is ok.
If you have other values you might need replace IC602.. any op is good for replacement like, 4558..etc
As I told you, if nothing happens, i.e. everything is ok, leave amp ON about 1hour, after sometime you check voltages in base of drivers. After 1hour, if is ok, then you put 1pnp and 1 npn on output and make sure prior connecting these trannies discharge your electrolytes for any unpleasant spark.
it should work.
bekim
sorry for late response, I was celebrating Independence of Kosova..
regarding optocoupler, you can use any TLP521 regardless of last markings..
if your transistor TR601 shows very low value in your digital multimeter, i think you have to replace it or "made" it as I told you previously. But, try something else:
- put in pcb all parts except output trannies..
- as well, drivers put in your pcb..
- turn your amp ON and measure the values on TR601 and on base of output trannies - both pnp and npn.
If now will not burn anything, this is ok.
If you have other values you might need replace IC602.. any op is good for replacement like, 4558..etc
As I told you, if nothing happens, i.e. everything is ok, leave amp ON about 1hour, after sometime you check voltages in base of drivers. After 1hour, if is ok, then you put 1pnp and 1 npn on output and make sure prior connecting these trannies discharge your electrolytes for any unpleasant spark.
it should work.
bekim
Hi Bekinbekim said:
Congratulations on the independence !!!
Can you explain the measuring I must do in TR601... ?
I have mounted averything on the pcb except the output trannies and left it working for more than two hours.... nothing burns and the values on the bases of the output are stable (+0.31v NPN -0.50v PNP).
I believe that now it will work.
Ricardo
ok,
these are good news.
Try to put just one pnp & one npn on output and see what happens, you can try some cheap trannies if you want.
check on Collector of TR601 voltage, I think it should be 80v, as well you said that you don't have symmetrical value on Bases of output trannies +0.31v NPN -0.50v PNP
hmmmm
I've to think...
these are good news.
Try to put just one pnp & one npn on output and see what happens, you can try some cheap trannies if you want.
check on Collector of TR601 voltage, I think it should be 80v, as well you said that you don't have symmetrical value on Bases of output trannies +0.31v NPN -0.50v PNP
hmmmm
I've to think...
Ric,
I checked your xls file, and you write that D508 conduct bothways, please, when you measure one diode or transistor remove it from pcb than you check with dmm.
D508 is connected in paralel with relay therefore it shows you bothways.
Unless you have +.5v & -.5v in bases I will not prefer to put any output trannies in your amp.
You can remove D512 & D513 and turn amp on and check for changes.
I checked your xls file, and you write that D508 conduct bothways, please, when you measure one diode or transistor remove it from pcb than you check with dmm.
D508 is connected in paralel with relay therefore it shows you bothways.
Unless you have +.5v & -.5v in bases I will not prefer to put any output trannies in your amp.
You can remove D512 & D513 and turn amp on and check for changes.
Hi Bekin
Without the diodes 512 513 I read -4.50V !!! almost everywhere:
In the bases of the trannies, on the bases of the drivers and TR510
On TR509 base I have -3.7v.
Also -4.5 ~~ -4.7 on pins 3 and 4 of IC 501.
I am afraid I will burn something more so I will but the zeners back in again.
Please give me your e-mail so I can send you some pics.
Regards
Ricardo
Without the diodes 512 513 I read -4.50V !!! almost everywhere:
In the bases of the trannies, on the bases of the drivers and TR510
On TR509 base I have -3.7v.
Also -4.5 ~~ -4.7 on pins 3 and 4 of IC 501.
I am afraid I will burn something more so I will but the zeners back in again.
Please give me your e-mail so I can send you some pics.
Regards
Ricardo
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