Need help on my kenwood basic m2 amp

[rmitch47]

speaker wires were wrong and blew fuse! Well i replaced fuse with fast acting one and it kept blowing them! A friend told me to replace it with a slow blow fuse because of the current surge at start up and now all the lights work , but no sound! Im hoping its nothing serious, can someone give me some ideas to narrowing the problem down so I tell if its worth fixing? I have had this old amp for years now and hate to trash it! Thanks

 

[Nigel Goodwin]

Presumably you've shorted the speaker wires and blown the amp?, if it's an IC output stage, you probably need to replace that IC (if it's still available).

 

[rmitch47]

Is there anyway to check if ic is damaged? Because I failed to mention, but I had a leaky cap and already replaced it( didnt show any signs of board damage). I can still get a ic if needed. I also have copy of schematic if you would like to take a look at what im dealing with. Thanks for the quick reply

 

[Nigel Goodwin]

If you've got a schematic, post it on here - click on 'Go Advanced' and 'Manage Attachments'.

 

[rmitch47]

Here it is. Thanks again I will bbl

 

[Nigel Goodwin]

It's mostly a discrete amp, for a start measure the voltages on the emitter resistors - both channels should be close to zero volts.

 

[rmitch47]

I opened the case to check voltage and found some burnt marks around transistors heat sinks, as you can see in the new attachment! Next I took the board out and tested the transistors surrounding the burnt spots, i found q26, q25,q27, where burnt up! The question now,do you think further testing is needed and if so, where should I go next? Again thank you for all your help, I will be ordering those transistors Monday! Oh also, I went to drain the caps before working on it and there was no charge to be discharged, I thought that was strange. Please let me know what you think. Thanks

 

[Nigel Goodwin]

If 25, 26, and 27 are all duff, then you've got bigger problems, because that's both channels that are blown.

I would be very doubtful that it's only those, drivers blowing with out the output transistors blowing as well would be VERY unusual.

As the entire power amp is DC coupled, anything which has been damaged and not replaced will most likely blow everything again. As a professional service engineer I would change ALL transistors in the DC chain.

 

[rmitch47]

OUCH!!! We talking about the DAT****P trans, you wouldnt happen to know where I can find the best deal on those? I only checked the transistors around the burnt area and only was able to test using a ohm meter. also will I need to worry about any resistors being burnt? Well I hate say it but do you think the slow blow fuse caused all this damage? Damn I could almost cry, best damn amp I ever had and has lasted for years! I hope I will be able to fix it, its looking like alot of work ahead! I tried to get on earlier today but I guess the forum was down! Hope to hear some good news from you on this amp or maybe some uplifting advise! LOL Thanks again hope you hang in here with me!

 

[rmitch47]

Nigel dont leave me please! I will need your help more than ever.

 

[Nigel Goodwin]

Unfortunately Kenwood pulled out of the UK years back, so there are no spares available here anymore

 

[rmitch47]

Unfortunately Kenwood pulled out of the UK years back, so there are no spares available here anymore

Well is there a way to check the DAT1521n and p transistor to make sure they are all bad, because these thing cost $50.00 a piece to replace in USA!
Also Nigel should I check anything else on board besides transistors? Thank man

 

[Nigel Goodwin]

You can check them statically, they are likely to be either S/C or O/C if they are faulty.

Also check resistors which are in places where the transistors could have damaged them (around the drivers and outputs).

 

[rmitch47]

You can check them statically, they are likely to be either S/C or O/C if they are faulty.

Also check resistors which are in places where the transistors could have damaged them (around the drivers and outputs).

Hey Nigel, I think this is good news, but wanted you to check it out before I buy it! Kenwood BASIC M2 M2A Output Stage Modification KitIt looks like everything im going to need and at a really good price! A guy on this forum found it for me and I was wondering your thoughts on this. It also looks like it may make my amp even better by what I read. Hope to hear from you soon, thanks again man

 

[Nigel Goodwin]

I had a look at it, it looks really good, just what you're looking for.

 

[john_m]

You can get all the parts you need for the M2 from here

UTSOURCE.NET

I have just recieved a a whole bunch of OEM parts in original sealed vacuum
packed anti static packaging, for an M2 I am repairing.

I pay $10.00 AU each for the DAT1521P DAT1521N, DAT1018P DAT1018N.
They also have the hard to get 2sc2590 transistor, I also grabbed two of the
TA2031 switching ic`s, and they can even get the hard to find zeners that kenwood
used on these amps.

Hope this helps.

 

[senile ancient hippy]

kenwood mod kit

Hey Nigel, I think this is good news, but wanted you to check it out before I buy it! Kenwood BASIC M2 M2A Output Stage Modification KitIt looks like everything im going to need and at a really good price! A guy on this forum found it for me and I was wondering your thoughts on this. It also looks like it may make my amp even better by what I read. Hope to hear from you soon, thanks again man

wondering if the mod kit worked out? considering purchase of the same amp to replace bryston 4b specs are similar right down to the weight of the amp.