C2A transistor equivalents?

[lowredmoon]

Have any of you had success replacing the 2SA913 and 2SC1913 transistors in a C2A preamp? If so, what did you use?

I pulled the 2 pairs from the tone control board and tested them on my simple GM328 transistor tester. 3 of the 4 test with an hFE of between 90 and 100. One of them tests at 33.

I tried swapping in 2SA1930 and 2SC5157 (very close specs but 50% higher gain and higher frequency) and now the preamp will not pass sound. I also replaced the 4 VD1212 on the tone control board with 2x 1N4148 in series (correct polarity) at the same time.

I have a full set of Nichicon capacitors coming from Mouser.

The original issue that prompted the parts swapping is loud popping coming from both channels, but not both at the same time.

If I can find appropriate replacements for the TO-220 transistors, I'm going to overhaul the whole thing, within reason.

 

[avionic]

Check the spec sheets on these.

2SC1913=KSC2073 or MJE15032
2SA913=KSA940 or MJE15033

 

[clinic-audio]

Hello

Have any of you had success replacing the 2SA913 and 2SC1913 transistors in a C2A preamp ? If so, what did you use ?

Replacing 2SA913 and 2SC1913 is not necessary if they are good . TR are not valves (tubes) and specifications will not "decrease" with the time .

I pulled the 2 pairs from the tone control board and tested them on my simple GM328 transistor tester. 3 of the 4 test with an hFE of between 90 and 100. One of them tests at 33.

Yes , maybe but it is not the cause of your trouble and your tester do not work under same voltages conditions ...

I tried swapping in 2SA1930 and 2SC5157 (very close specs but 50% higher gain and higher frequency) and now the preamp will not pass sound.

Yes this is normal , if you have any DC voltage at the output ! in this case the output is muted , so no sound at the output .

I also replaced the 4 VD1212 on the tone control board with 2x 1N4148 in series (correct polarity) at the same time.

Yes , I already post about this subject sometime ago and again 2 1N4148 in serie is not perfect sub for VD1212 . 1N4148 are diodes , VD1212 is varistor , not really the same thing . I know that many people do this on the web but it is not equivalent .......And will not cure your problem

I have a full set of Nichicon capacitors coming from Mouser very good , this is the first thing to do and first all the green cap (you will see the corrosion on the legs)

If I can find appropriate replacements for the TO-220 transistors, I'm going to overhaul the whole thing, within reason.

I don't think that replace all TO220 transistors in this unit with this trouble will clear your trouble .

Many soldering in this unit need to be redone (class A , heat and years make them really critical )

Check all voltages first and follow all adjustments procedure carefully in right order

You can replace all trimmers if you want

Regarding your trouble , think about the fact that you can spend hours and hours before to find the gulty part .....Sometime C2A are not easy to do

 

[lowredmoon]

Check the spec sheets on these.

2SC1913=KSC2073 or MJE15032
2SA913=KSA940 or MJE15033

Thank you. Do you know whether the transition frequency is relevant in this circuit?

 

[lowredmoon]

Replacing 2SA913 and 2SC1913 is not necessary if they are good . TR are not valves (tubes) and specifications will not "decrease" with the time .

I did not know this. Do they go intermittent or just fail completely when they go?

Yes , I already post about this subject sometime ago and again 2 1N4148 in serie is not perfect sub for VD1212 . 1N4148 are diodes , VD1212 is varistor , not really the same thing . I know that many people do this on the web but it is not equivalent .......And will not cure your problem

Do you know of any true equivalents that are available? I made the grand mistake of losing 3 VD1212 that I pulled out. I recovered one of them. I may have to paw through junked receivers to find them. A seller on eBay wanted $6+$4 shipping a piece for them. Wow!

I don't think that replace all TO220 transistors in this unit with this trouble will clear your trouble .

Many soldering in this unit need to be redone (class A , heat and years make them really critical )

Check all voltages first and follow all adjustments procedure carefully in right order

You can replace all trimmers if you want

Regarding your trouble , think about the fact that you can spend hours and hours before to find the gulty part .....Sometime C2A are not easy to do

When I receive the capacitors, I'll go back to square 1 and proceed more patiently. This C2A was given to me for free because it had problems. It is the nicest preamp I've ever owned. I want to treat it well.

Adam

 

[clinic-audio]

Hello Adam

Do you know of any true equivalents that are available ? YES
When I receive the capacitors, I'll go back to square 1 and proceed more patiently. Yes , do the green first
This C2A was given to me for free because it had problems yes , I am sure that the first tech who tried to refix this trouble spend probably 2 days without success and give up ! that's why the previous owner's give it to you ...on every C2A I did , one make me loose too much time to find the reason why .Not permanent problem and very costly in time in a business point of view and the most important "never undertood by the owner "
Did you check all soldering on the both boards ?
It will take you maybe one complete day to make them well redone like new .
See the green cap on my pictures




How many DC Volt do you have there :

 

[lowredmoon]

Do you know of any true equivalents that are available ? YES

Are you willing to share this info?

Yes , do the green first]

I ordered replacements for all the green electrolytics.

yes , I am sure that the first tech who tried to refix this trouble spend probably 2 days without success and give up ! that's why the previous owner's give it to you ...on every C2A I did , one make me loose too much time to find the reason why .Not permanent problem and very costly in time in a business point of view and the most important "never undertood by the owner "
Did you check all soldering on the both boards ?
It will take you maybe one complete day to make them well redone like new .
See the green cap on my pictures

Fortunately, this is a recreational project for me, and not business (though that is obvious), but I understand what you mean. The previous owner is an electrical Engineer who doesn't like fixing equipment - only building it.
I visually inspected the solder joints. I am cautious about re-soldering everything because I'm concerned about applying heat to all the components. But if that's what must be done, I'll do it.

Thank you for you replies! Merci!

 

[clinic-audio]

2 1N4148 in serie give :



1 VD1212 give :



perfect sub for VD1212 is MV12 YAMAHA part number IF000790

 

[Mr. Yamaha]

perfect sub for VD1212 is MV12 YAMAHA part number IF000790

View attachment 912687

Yes you keep repeating that in numerous threads, but the MV12 is also not available and you do not share you source. So, what's point of telling people about this mysterious substitute which they can't source?

 

[zaibatsu]

I visually inspected the solder joints. I am cautious about re-soldering everything because I'm concerned about applying heat to all the components. But if that's what must be done, I'll do it.

I wouldn't worry about that, the solder joints in old Yamaha gear (particularly Class A as mentioned, eg. most preamps) are the cause of many problems - and in my experience joints can be bad even when they look OK visually. I find it's good to touch the joints with some fresh solder too.

Generally the biggest culprits are transistors, and fortunately they are designed for heat. The only components you should be careful with when resoldering are polystyrene caps - they are the clear plastic vertical cylinders with winds of foil inside, usually silver or copper foil. They can't take much heat so work fast.

 

[lowredmoon]

I wouldn't worry about that, the solder joints in old Yamaha gear (particularly Class A as mentioned, eg. most preamps) are the cause of many problems - and in my experience joints can be bad even when they look OK visually. I find it's good to touch the joints with some fresh solder too.

Generally the biggest culprits are transistors, and fortunately they are designed for heat. The only components you should be careful with when resoldering are polystyrene caps - they are the clear plastic vertical cylinders with winds of foil inside, usually silver or copper foil. They can't take much heat so work fast.

Thanks for the tips. I actually ordered some good 220pF Wima film caps in case I would happen to ruin any of the ones on the board -- which is to be avoided, of course, but they're useful for other projects as well.
I'm looking forward to digging in to it this weekend!

 

[lowredmoon]

2 1N4148 in serie give :

Thank you for posting your data and replacement part.

 

[clinic-audio]

Yes you keep repeating that in numerous threads, but the MV12 is also not available and you do not share you source. So, what's point of telling people about this mysterious substitute which they can't source?

There is no mysterious substitute , they are sold to official service stations only . You have the part number . You can act now .

 

[Mr. Yamaha]

There is no mysterious substitute , they are sold to official service stations only . You have the part number . You can act now .

Let me guess, you own an 'official service station' and we don't, so we can't get it. How does that help the TO?

Have you ever googled the part number you provided (again)? It doesn't point to a place where they can be bought.

Or are you trying to lure potential customers to your own 'official service station'? I'm a bit confused here.

Anyway, same popo, different thread

Sorry lowredmoon, for this thread pollution

 

[lowredmoon]

Sorry lowredmoon, for this thread pollution

No problem.
Hey, if he knows of an equivalent of a part I'm having a hard time finding, I want to hear about it, even if it is also hard to locate.

 

[Vint Age]

Hey, if he knows of an equivalent of a part I'm having a hard time finding, I want to hear about it, even if it is also hard to locate.

Agreed!

 

[lowredmoon]

How many DC Volt do you have there :

View attachment 912430

+35VDC at TP3. No variation with adjustment of VR501.
Between +/- 40mVDC at TP1.
I checked for shorted film capacitors in the area, all are OK. I changed TR527 and TR529. Still 35V.

 

[clinic-audio]

OK
Thank you very much to answered to my question but you don't with the other one .
Did you "remade" all the soldering on this long board ? this is a VERY long process , but you have to do it.
Again your problem is not coming from a TR or a capacitor .I have refixed many C2A and this is different for each one but many has the same phenomenon . Despite the comments of one member , I have enougth experience to give you the appropriate advise in these post .
As I said the other day , you can spend hours and hours (sometime days!) before to find the reason why , so stop to loose your time in other directions if you want to bring it back to normal function !.
Most important thing : follow advise from people who knows not from people with low level of experience .
Once you did this come back to us with report . If you are not successfull I will give you another instruction .

 

[lowredmoon]

Thank you for your input.
No, I haven't reworked the solder joints yet. I'm going to do that over the weekend. In fact, I used this very project as a reason to buy a better soldering iron.

 

[lowredmoon]

While I'm reworking the solder, do you have any words of advice on cleaning the sealed volume and tone controls? I own many different electronics cleaners, including all Deoxit products.