Hello,
once again my limited knowledge leads me here hoping for enlightenment 🙂
I'm currently rebuilding a sansui 5000x based on a seemingly professional blog I found. This includes replacing small signal transistors on the eq, tone and driver boards and a few more psu related ones. I'll be using ztx694b and ksc1845fta.
I noticed the input pair of each board has a red or white dot on the top which probly indicated matched pairs so now I'm stuck with the question if I should leave those matched input transistors in place and only replace the remaining ones or not. I dont have a circuit for matching transistors I just have a peak dca55 and found pairs (ztx and ksc) which have identical hfe and vbe but I'm not sure if thats enough to call it a matched pair yet...any opinions welcome...leaving all transistors original is not an option though, the amp had popping noises which I think are related to the 458 tranaisors in the tone amp and also now that I got those relatively expensive ztx ones theres no way I wont use them...hoping for advise on the matching issue 🙂)
once again my limited knowledge leads me here hoping for enlightenment 🙂
I'm currently rebuilding a sansui 5000x based on a seemingly professional blog I found. This includes replacing small signal transistors on the eq, tone and driver boards and a few more psu related ones. I'll be using ztx694b and ksc1845fta.
I noticed the input pair of each board has a red or white dot on the top which probly indicated matched pairs so now I'm stuck with the question if I should leave those matched input transistors in place and only replace the remaining ones or not. I dont have a circuit for matching transistors I just have a peak dca55 and found pairs (ztx and ksc) which have identical hfe and vbe but I'm not sure if thats enough to call it a matched pair yet...any opinions welcome...leaving all transistors original is not an option though, the amp had popping noises which I think are related to the 458 tranaisors in the tone amp and also now that I got those relatively expensive ztx ones theres no way I wont use them...hoping for advise on the matching issue 🙂)
The usual reason for using matched pairs is lower distortion ( of one kind or another ) , this is achieved by roughly the same method you used to measure your "matched pairs " --same gain etc which costs dearer if buying them matched .
I too have both Peak testers which are pretty accurate if you keep checking for updates ,
The main thing is do the matched pairs already on the board "match up " with the ones you are going to install --in specification?
The ones you have might be matched but are they near the same parameters as the ones in your amplifier ?
I too have both Peak testers which are pretty accurate if you keep checking for updates ,
The main thing is do the matched pairs already on the board "match up " with the ones you are going to install --in specification?
The ones you have might be matched but are they near the same parameters as the ones in your amplifier ?
Thanks for the reply 🙂 Is it possible to manually update the peak firmware? I though they have to be sent to the manufacturer to do so...?
I will check the gain of the original transistors and see what hfe they are and if I have a similar pair of the new ones. would there be any disadvantage in leaving the original matched ones in place and replacing all others?
I will check the gain of the original transistors and see what hfe they are and if I have a similar pair of the new ones. would there be any disadvantage in leaving the original matched ones in place and replacing all others?
Your right , shows how out of date I am they now charge for an update .
If I was in your position I would leave the original BJT,s in place they are the old original ones with high audio spec. especially low noise , the more modern ones of the same coding aren't as good as they are.
If I was in your position I would leave the original BJT,s in place they are the old original ones with high audio spec. especially low noise , the more modern ones of the same coding aren't as good as they are.
yes, I will most likely leave the input pairs as they are and just replace the remaining ones...chances that the noisy one is amoung the not matched ones is higher than the chances that I'm finding a pair matched as well as the ones matched at the factory I guess...it's just this feeling of not having completed the service task but I think I can convince my head that its for the better this way. Will keep the closest pairs packed together just in case I'm still having those noises when it's all done.
Thanks for your advise!!
Thanks for your advise!!
Replace and listen one by one. Where it needs to be replaced in pairs. Input transistors are usually noisy. Start with them.
Consider the possibility of a different pinout of modern transistors for replacement.
Do not overheat the transistors when soldering. Try to do it faster. Use tweezers.
Consider the possibility of a different pinout of modern transistors for replacement.
Do not overheat the transistors when soldering. Try to do it faster. Use tweezers.
Any good test bench has a signal tracker on it to determine where in a circuit there is an issue.
Instead of guessing, which is a foolish waste of time.
Instead of guessing, which is a foolish waste of time.
Perhaps, use heat and freeze spray to find the offending device. Anyone who's ever tried replacing every, or even most, of the transistors in a big, mostly-discrete vintage amp will tell you, 'between mistakes (flipped or different pinouts) and unsuitable substitutes (data sheet hFE matches are Not Matched), you will spend considerably more time, money, and frustration by the time it works properly again, than if you simply find and fix the problem.
I would be highly suspicious of the 'seemingly professional blog'. What you're planning would be a worthy challenge for a highly experienced tech with a full compliment of test equipment and spare parts. And it would still take a lot longer; and it would not yield the hoped-for sonic improvement.
Just my 2 cents ..😉
Cheers
I would be highly suspicious of the 'seemingly professional blog'. What you're planning would be a worthy challenge for a highly experienced tech with a full compliment of test equipment and spare parts. And it would still take a lot longer; and it would not yield the hoped-for sonic improvement.
Just my 2 cents ..😉
Cheers
I tend to agree with Rick about those 'seemingly professional blogs' he mentioned.
I've done restorations on enough of 5000's, including the first ones that were famous for blowing boards, up to the "X" models.
If they were in working condition, I seem to recall that I never had to replace transistors, only the usual electrolytics, rarely even a resistor, maybe some dial lamps.
And they all came out with the performance that they're known for.
I've done restorations on enough of 5000's, including the first ones that were famous for blowing boards, up to the "X" models.
If they were in working condition, I seem to recall that I never had to replace transistors, only the usual electrolytics, rarely even a resistor, maybe some dial lamps.
And they all came out with the performance that they're known for.
Sansui 5000X AM/FM Stereo Tuner Amplifier Manual | HiFi Engine
Since 1971, there is a lot to service besides electrolytes and transistors. Soldering can become unreliable, switches and controls worn out. Contacts are oxidized. Calmly and methodically try to isolate the problem. Correct the found flaws.
Since 1971, there is a lot to service besides electrolytes and transistors. Soldering can become unreliable, switches and controls worn out. Contacts are oxidized. Calmly and methodically try to isolate the problem. Correct the found flaws.
First of all thank you all for your input! Maybe just have a look at what I'm talking about and tell me if it's total bs or not...I tend to think they know what they're doing there...
Vintage Hi-Fi Audio Restorations: Shaans Sansui 5000X Restoration
Vintage Hi-Fi Audio Restorations: Shaans Sansui 5000X Restoration
I agree replacing the transistors probably is not necessary, and might cause more problems than it solves. it is probably good enough just to touch up the solder joints, if that.
Where did you find this out and what transistors specifically do you mean? I know that the original 2SC1815/2SA1015 specify <50/30 ohms base resistance in the datasheet, but modern versions curiously omit this field.
Where did you find this out and what transistors specifically do you mean? I know that the original 2SC1815/2SA1015 specify <50/30 ohms base resistance in the datasheet, but modern versions curiously omit this field.
It might come as a shock to you but I dont even have a test bench, just a living room table, a scope, dmm and the dca55 and a whole gallon of finest snake oil to drown my amps in...I understand if you think I shouldnt be touching vintage gear with this rather unprofessional attempt but just like the bumble bee flies, I tend to be successfull with my restorations, it just takes longer as I have to ask questions like the one I'm asking now in order to confirm or discard things I find on the web before applying all the snake oily goodness 😉 I agree that a signal tracer would be a nice addition to my living room table though 🙂
I would only replace transistors that were actually likely to fail like the 2SC458. For anything else I would want to see the schematic as it's not as simple as new transistor = better performance. If it sounded good to begin with, why throw all that up in the air by changing the transistors? If it didn't sound good enough with the original transistors then why does anyone care about it in the first place?
I'm not especially chasing for better sound, the 5000x sounds great as it is but as I said it has this popping/clicking noises after a while of listening and since I have it open and disessembled in order to take all the switches etc apart to clean them and stumbled upon the blog I posted the link of I thought why not replace all the parts which are prone to failure like 2sc458... if one went bad its only a matter of time until the others might follow. The blog reads like the people who wrote it do have some knowledge and also they show their measurments so I assumed there's nothing wrong with just doing what they did.
I admit it would've been smarter to ask for opinions on what they did prior to ordering all the parts...
Well if no one complained about the sound afterward it's likely it turned out fine. In this case it's better not to worry about things beyond your control. Maybe you can make a decision based on resale value. Will it sell for more with the original transistors or with new replacements?
It would be interesting if someone compared an original to one which had been restored with new transistors.
It would be interesting if someone compared an original to one which had been restored with new transistors.
Yes I agree, a comparison would be nice...thats the reason why I have 4 Nad 3020 as thats one of those amps most prone to snake oil restorations and I wanted to compare different setups/components and see how a stock rattle snake compares to a overblown silmic/wima polyprop Cobra...didnt have the time yet. The problem I have with this blog is that they do tell what has been changed etc but of course not in great detail so who knows if they spent hours finding the right matching transistors and whatnot, so a non professional like me can either hope for the best or ask people with more knowledge...did you take a look at the link I posted? Does it look reasonable for your understanding or are they just lucky the whole thing didnt blow up in their faces? resale value is not really a point for me, I'm gonna keep this one but also I kept all the parts I removed...just in case...
I think I will try it with replaced transistors and if it still makes me smile I'll leave it...you see that how much of a professional I am...For me theres two categories of amps...the ones that make me smile and listen to music all night long and the ones that don't...the 5000x made me smile a lot...untill it began popping around...
Popping noises, in my experience, can stem from intermittent resistors, coupling capacitors, solder joints, and in rare cases, transistors.
Just because "someone on the internet" in some blog says to replace a certain transistor, doesn't mean a thing to me.
I tend to distance myself from those "internet specialists" and "advisers" because I don't know their real background, schooling, and qualifications, despite what they might say or do.
I only know for sure my own portfolio.
Just because "someone on the internet" in some blog says to replace a certain transistor, doesn't mean a thing to me.
I tend to distance myself from those "internet specialists" and "advisers" because I don't know their real background, schooling, and qualifications, despite what they might say or do.
I only know for sure my own portfolio.