PD1515 NPN Bipolar Transistors & its Data !

[reubensm]

To answer your query on Germanium power transistors, I am familiar with the following (dad used these at some point)

AC 127 - AC 128 for small 1 watt amplifiers
AC 187 - AC 188 pair for small 3 watt amplifiers (my first amplifier that I built in standard-4, still have it and my brother's son used it to win a second price during a recently concluded science exhibition )
Philips - PT4 and PT6 (a stereo amp with 2 pairs of these as output transistors could deliver about 5+5 watts)
AD 161 - AD 162 similar to PT4 and PT6
AD 149 could be used as a pair to rake up 15-20 watts per channel

Those were fun days

 

[reubensm]

On another note, the output transistors look absolutely soiled and the heatsink compound with thermal conductivity looks absolutely dried out. You will have to carefully remove the output transistors, clean up the thermal contact surfaces, apply fresh heatsink compound and screw them back. Be careful with the insulation as the housing of these metal cap transistors is of course, the collector.

 

[yugaaa]

A note from my experience. I have finished restoring a badly tampered with NAD 3020 which had loads of Jugaad repairs done on it. One of the 2N3055 output transistors, the one on the left channel, had been replaced with a Chinese one. This channel was sounding dull and there was clear channel imbalance as a result I had a Motorola 3055 transistor which i had kept in my collection as a replacement for my 3020 and was able to replace this Chinese 3055. The moment this replacement happened, the concerned channel returned to normal the channel imbalance disappeared. So in this case, using an original Motorola replacement did the trick

most chinese fakes are actually low powered cheaper transistors . The indian ones are fine .

 

[yugaaa]

That picture of all 4 output transistors reveals the plot. Your amp originally had 4 x PD1515 output transistors. One of them would have been replaced and that's why the BUX39 from Electronics Corporation of India (ECIL, with the EC logo) features there. It is also now confirmed that the PD1515 transistors must surely be NPN. That also ties up with the fact that your drivers are SL100-SK100 pairs.

Now to my suggestion (again this is my humble opinion and what I would have done if I were to fix this Indian legend):

You are not likely to find the PD1515 transistor any more. However you will find the MJ 15015 (or MJ 15015G) metal cap transistor which can be used as a direct substitute.

This transistor was manufactured originally as the PD 15015 transistor but these days, you are most likely to find the MJ version. Just as we come across the 2N 2955 - 2N 3055 Pair (with 2955 being PNP and 3055, NPN), the 150xx series appears as MJ 15015 - MJ 15016 (with 15015 being NPN and 15016, PNP). Also if you look at the data sheets and do a comparison, the MJ 150xx series comes with same specs as the 2N3055A (which has greater tolerances when compared to the 2N3055). Please take a look at this.

Hope this helps

If we go by the data sheet and assumption that PD1515 might in fact be 2sd2488 then it is a darlington . The driver transistors are germanium here and their wattage would be limited to driving a darlington .

 

[yugaaa]

B.Just like higher Micro Farad/uf, can't we use higher voltage capacitor of 400-500V?
You will end up spending more money than necessary . Higher voltage caps cost more . hehe

C.If used what are the drawbacks?[/QUOTE]
No drawbacks. In fact better if carefully chosen .

A.Really? a Darlington? Is this type of Transistor can be used wher bipolar transistor are implemented ?
Darlingtons have a high gain ratio compared to normal transistors . When was the bux39 changed ? After the change was the amp performing ? I have a strong notion that the Bux 39 never worked . Even if it worked , the person who did the job .. should have been changed in pairs .

B.Is Darlington superior to Bipolar?

A. Of right Channel? If so I'll ask uncle to check.
Any channel . Just measure the transformer secondary voltages .



C.Don't know but as I said previously everything blew in left channel except the fuses I guess or else the catastrophe could have not happened. :-(

But I see blown fuses in the pics ..

I also suggest that you resolder the whole amp . There will be quite a few dry solder joints

 

[jls001]

Higher voltage caps cost more . hehe

To add: higher voltage caps are bigger in size, so depending on available space it may or may not be feasible to use higher voltage rated caps.

 

[reubensm]

Forgot to mention, my inference and opinion is based on the component values visible, their placement on the PCB and old-school knowledge based assumption of how the components bearing these values would be wired on the other side of the PCB. Given the fact that one of the PD1515s was replaced with the BUX39, the PD1515s definitely cannot be Darlingtons in my opinion.

Also I have only commented only on the output transistors. My approach to repair (if I was working on an amp) would not include "repair" but "restoration" which includes a complete check up of everything on the PCB, re-capping, soldering, etc. Also in older amps, especially in India, there is bound to be some level of equivalent or quick-fix based repair conducted at some point. Reversal of these, to OEM standards is what I usually try to do.

 

[Danieljohn]

To answer your query on Germanium power transistors, I am familiar with the following (dad used these at some point)

AC 127 - AC 128 for small 1 watt amplifiers

In a Single Ended Circuit? Sir.

AC 187 - AC 188 pair for small 3 watt amplifiers

In a Push Pull Circuit? Sir.

(my first amplifier that I built in standard-4, still have it and my brother's son used it to win a second price during a recently concluded science exhibition )

That's Amazing ! To know. :-D

Philips - PT4 and PT6 (a stereo amp with 2 pairs of these as output transistors could deliver about 5+5 watts)
AD 161 - AD 162 similar to PT4 and PT6

I believe in a Push-Pull Topology.

AD 149 could be used as a pair to rake up 15-20 watts per channel

A.In a Single-Ended Topology?

B.Are AD 149 the biggest Germanium Transistor? Sir.

Those were fun days

Yeah !
I experience those days by listening to that period music through vintage gear then automatically I start seeing things of those days.

 

[Danieljohn]

On another note, the output transistors look absolutely soiled and the heatsink compound with thermal conductivity looks absolutely dried out. You will have to carefully remove the output transistors, clean up the thermal contact surfaces, apply fresh heatsink compound and screw them back. Be careful with the insulation as the housing of these metal cap transistors is of course, the collector.

Thanks Dear Reuben Sir,
I won't be doing these things myself but I indirectly tell my Sound Engineer Uncle (If I say this directly he will kill me with lecture) who is taking care of my Amplifier now after soo much of requesting.

 

[Danieljohn]

most chinese fakes are actually low powered cheaper transistors . The indian ones are fine .

I 100% agree with you Dear Yugaaa,
But my point really was not just about counterfeit or Chinese Transistors but two Different Original Transistors with obviously different characters/natures in a same Amplifier.

 

[Danieljohn]

If we go by the data sheet and assumption that PD1515 might in fact be 2sd2488 then it is a darlington .

Dear Yugaaa,
A.Did you found PD1515 Data???

B.If so kindly let me know about it

C.Darlington Transistors can be implemented wher Bipolar Transistors are in use? I mean in a same Circuit Design/Topology both type of Transistors could be implemented ?

The driver transistors are germanium here and their wattage would be limited to driving a darlington .

What made you assume that Driver Transistors could be Germanium?

Infact I feel that pretty Strongly !
bcuz of the Amazing SQ.

 

[Danieljohn]

A.Just like higher Micro Farad/uf, can't we use higher voltage capacitor of 400-500V?

You will end up spending more money than necessary . Higher voltage caps cost more . hehe

B.If used what are the drawbacks?
No drawbacks. In fact better if carefully chosen .



C.But I see blown fuses in the pics ..

I also suggest that you resolder the whole amp . There will be quite a few dry solder joints

A. Ok but would it be any Good for anything?

B.How to choose carefully & what exactly you implied? I mean the Parameters or things which really matters.

C.Yeah no doubt !

Thanks for Inputs Yugaaa.

 

[Danieljohn]

To add: higher voltage caps are bigger in size, so depending on available space it may or may not be feasible to use higher voltage rated caps.

Dear Jls001,
If I find the right size with 400-500V cap which can be accommodated within the amplifier would ther be any possibility of any kind of danger to the Amplifier? Or will it help in someway?

Thanks for your Support !

 

[Danieljohn]

Forgot to mention, my inference and opinion is based on the component values visible, their placement on the PCB and old-school knowledge based assumption of how the components bearing these values would be wired on the other side of the PCB. Given the fact that one of the PD1515s was replaced with the BUX39, the PD1515s definitely cannot be Darlingtons in my opinion.

A.Dear Reuben Sir pls don't make me Sad by using words like "Interference" your kind helpful inputs are extremely valuable to me.

B.Yes I too believe that PD1515 can't be Darlington bcuz I really don't know whether Darlington Transistors can be implemented wher Bipolar Transistors are in use.

C.But if Darlington can be used wher bipolar transistor are implemented & if Darlington Transistors are Superior to Bipolar then I 100% Believe that PD1515 Could be a Darlington or Germanium for that matter.

Also I have only commented only on the output transistors. My approach to repair (if I was working on an amp) would not include "repair" but "restoration" which includes a complete check up of everything on the PCB, re-capping, soldering, etc. Also in older amps, especially in India, there is bound to be some level of equivalent or quick-fix based repair conducted at some point. Reversal of these, to OEM standards is what I usually try to do.

That's Amazing but would you recap even the original caps which are in Good condition & same Caps are not available anywhere too?

 

[jls001]

Dear Jls001,
If I find the right size with 400-500V cap which can be accommodated within the amplifier would ther be any possibility of any kind of danger to the Amplifier? Or will it help in someway?

Thanks for your Support !

The original caps are already correctly rated for the voltage they will be used at. If for example the rail voltage of the amp is +/-35V, a 63V cap would have sufficient headroom so using a 100V won't offer benefits (all that headroom will go unutilised).

More than higher voltage, more relevant ratings would be the temperature rating (say, you use 105°C rated if it's already using 85°C rated ones), and, to an extent, lower ESR caps are desirable. Higher temperature rating will make it last longer in a harsher environment. A lower ESR will make the output impedance of the power supply lower (assuming you use it in the PSU section).

 

[Danieljohn]

The original caps are already correctly rated for the voltage they will be used at. If for example the rail voltage of the amp is +/-35V, a 63V cap would have sufficient headroom so using a 100V won't offer benefits (all that headroom will go unutilised).

By using a 400-500V caps would ther be any possibility of danger to the Amplifier?

More than higher voltage, more relevant ratings would be the temperature rating (say, you use 105°C rated if it's already using 85°C rated ones), and, to an extent, lower ESR caps are desirable. Higher temperature rating will make it last longer in a harsher environment.

By using higher temperature rated caps would ther be any possibility of danger to the Amplifier?

A lower ESR will make the output impedance of the power supply lower (assuming you use it in the PSU section).

A. Lowering the PSU Output impedance will help? Or Improve somethings?

B.Yes in PSU Section.

 

[reubensm]

A.Dear Reuben Sir pls don't make me Sad by using words like "Interference" your kind helpful inputs are extremely valuable to me.

B.Yes I too believe that PD1515 can't be Darlington bcuz I really don't know whether Darlington Transistors can be implemented wher Bipolar Transistors are in use.

C.But if Darlington can be used wher bipolar transistor are implemented & if Darlington Transistors are Superior to Bipolar then I 100% Believe that PD1515 Could be a Darlington or Germanium for that matter.



That's Amazing but would you recap even the original caps which are in Good condition & same Caps are not available anywhere too?

Sorry but I meant "inference" or understanding

Its a myth that caps will last forever. Recapping does not mean, blindly carpet-changing all the electrolytic caps (but this approach can also be taken, and is the best bet in my opinion). One has to properly check each electrolytic caps using an ESR meter. Over a period of time, the ESR value of electrolytics tends to increase and these caps with higher than normal ESR values are the ones to be replaced. Again recapping is a catch-20 decision as it can change the sound signature. Significant burn in is required to match the sound signature achieved by years and years of functioning. Alternatively, choosing not to recap can result in either deterioration of performance or even failure of the amplifier.

On an outside note, are you attempting to repair the amp or restore it, or just trying to accumulate as much info as possible on it. Just curious

 

[reubensm]

In a Single Ended Circuit? Sir.
Something on these lines

In a Push Pull Circuit? Sir.
This is the exact circuit

A.In a Single-Ended Topology?
Kind of like this circuit but with a few mods.

B.Are AD 149 the biggest Germanium Transistor? Sir.
These are the biggest ones I have experience with.

Current work bench:

NAD 3020 x 2
NAD 208 x 1
Sony 29 Wega Trinitron CRT TV x 1
Keltron 14 BW TV x 1
Garrard RC 210 x 1
Pioneer PL12 x 1

on the way for repairs

6L6 mono tube amplifier x 1
Akai 1710L tube r2r x 1
NAD 3020 x 1

 

[Danieljohn]

A.Sorry but I meant "inference" or understanding

LOL ! You know about me so no worries. ;-P

B.Its a myth that caps will last forever. Recapping does not mean, blindly carpet-changing all the electrolytic caps (but this approach can also be taken, and is the best bet in my opinion). One has to properly check each electrolytic caps using an ESR meter. Over a period of time, the ESR value of electrolytics tends to increase and these caps with higher than normal ESR values are the ones to be replaced. Again recapping is a catch-20 decision as it can change the sound signature. Significant burn in is required to match the sound signature achieved by years and years of functioning. Alternatively, choosing not to recap can result in either deterioration of performance or even failure of the amplifier.

I 100% agree with you in every aspect you mentioned.

C.On an outside note, are you attempting to repair the amp or restore it, or just trying to accumulate as much info as possible on it. Just curious

C.Restore to Original Condition or else I would have adjusted with Original Motorola 2N3055/2N3773 Transistors why would I go gaga over PD1515 & every microscopic thing.
Infact you all know how Mad I'm after Cosmic & yes all the accumulated inputs from you all will help me retain my amplifier's originality.

 

[jls001]

By using a 400-500V caps would ther be any possibility of danger to the Amplifier?

By using higher temperature rated caps would ther be any possibility of danger to the Amplifier?

A. Lowering the PSU Output impedance will help? Or Improve somethings?

No, there is no danger in using higher voltage rated cap. Just follow the polarities correctly. Ditto for higher temperature caps.

The PSU can be viewed as an independent electrical circuit, and like any circuit a lower output impedance is better than higher.