Sansui 5000a blows right channel fuse

[Lonnie]

Hi all, been lurking here for a while and decided to make a first post. I've always liked tinkering with electronics including a very large collection of old radios I have assembled over the years although I never got very good at fixing them I still enjoy it. Anyway to my question, I picked this receiver up (for free) and was under the impression that it worked, I was just going to replace all the blown bulbs and jam out some vintage Neil Young on this great vintage receiver, well guess what, it no workie. The right channel fuse blows immediately when switching on the power, even with no speaker connected. The left channel works fine. I checked for a short at the speaker connections, OK there. There are four large caps (22000uf 80volt) two for each channel I think. After unpluging there is voltage present at what I believe are the left channel caps but none on the right. Thanks in advance for your help.

[dood]

Re: Sansui 5000a blows right channel fuse

Sounds like a dead short in the right side somewhere, but I suppose you would've guessed that.

The caps discharging is tell-tale.

[Lonnie]

Re: Sansui 5000a blows right channel fuse

Must have gotten a little trigger happy, the caps are 2200uf but I'm sure you knew that!!

[mbates14]

Re: Sansui 5000a blows right channel fuse

sounds like shorted output transistors.

[Lonnie]

Re: Sansui 5000a blows right channel fuse

sounds like shorted output transistors.

Thanks, that's what I figured after looking around here http://audiokarma.org/forums/forumdisplay.php?f=39

[starfury1]

Re: Sansui 5000a blows right channel fuse

Id say so shorted output trannies...

I suppose the bigger question would be what killed it/them in the first place.

I would check them first off

Not having looked a schematic and me not knowing when it was made or its specs

I would guess the supply is "common" to both channels and maybe of Plus/Minus type
(if there are no large electro caps in the Power Amp output line to speaker.)

So the supply (if it does power both channels) should be ok if the left side is working ok

If you know how to use a multimeter to check transistors and can solder shouldn't be that hard to fix.

Although you may have to search for info on biasing the transistors and that would depend on how they designed it in the first place.

Getting exact transistor replacements might be a bit of a bother and you may have to search out Equiv replacement type...

I would give the pcb a good visual check and me would rework any high current or components that get hot like power resistors or output transistors that are bolted to heatsinks....depending on age and abuse other components may well need replacing, like caps

suppose it depends on how far you want to restored it
if it is a few years old and it sound like its in the restore class of items

That site look as if its worth searching

anyway good luck with it and this is just my thoughts on it

[mbates14]

Re: Sansui 5000a blows right channel fuse

about 85% of the time when the output transistors goes shorted, it takes out the transistor's driver transistors and sometimes nearby resistors.

chances are, only 1 output is shorted. becuase if they both were shorted, it would take the main B+ fuse and neither channel would be working, as its a rail to rail short.


Now if one shorts, it shorts ether V+ or V- to output, blowing the output fuse. but you replace both.

[capskiller]

Re: Sansui 5000a blows right channel fuse

Hi, I had the same problem with my Sansui 4000.
I'am not sure if both receivers are similar.
A dead ELNA cap on the driver board killed
a transistor which in turn killed output transistors.
The original ELNAs are now 30 years old.
Replace'em.
Mail me the sansui number of your damaged board if you like.

Jo

[JimHarry]

Re: Sansui 5000a blows right channel fuse

Hi, new guy here...I have a Sansui 5000A (bought while in Nam) now has a modified 1040 board, the other channel is orginal and doesn't work...I also have a 5000X that I purchased several years ago on eBay with F6013 boards but one channel is out. Can I make one good unit? Any pitfalls? Open to any and all suggestions. thanks Jim

[booksmusicetc]

Re: Sansui 5000a blows right channel fuse

If one channel is dead, most likely the output Xistor or push pull pair of xistors are shorted. It is possible, but unlikely, that a fusistor is in the output stage amp design, or
better yet a fuse! You may have gotten lucky and saved the output Xistors for that channel. Without checking the diagram, I am not sure what circuitry is there.
The usual cause of this problem is sloppy wiring to that channel speaker! Frayed wiring or stray strands touching the opposite pole connection is extremely common. If the wires to the speakers are long, you need to check the wire for fraying or stray strand shorting at dried out areas of the speaker wiring connection wires.
I would think it would be cheaper at this point to pick up a non working unit and use the output PC board or Xistors. Remember! Constantly check for low ohmage shorts on everything.!
I have a good working 5000A for sale at www.booksmusicetc.net (probably more than
you want to pay though) If I find another cheaper I will advise. Thanks and good luck!

[hardwareguy]

Re: Sansui 5000a blows right channel fuse

I'm going to be in agreement here.

When I see this, I head straight for the output transistors if it blows speaker fuses.

If its indeed a speaker fuse, it should not blow without a speaker attached. You should see much less than 1V DC from the + and - speaker terminals to the chassis ground. If there's any significant voltage, the outputs are shorted.

Sometimes a speaker fuse is an amp supply fuse...these can blow without speakers attached.

Check the outputs, the emitter resistors and the drivers. If any mica insulators are cracked, do not reuse them. Check the tightness of mounting screws before the lid goes back on....it's rare but I've seen stereos blow up because the screws loosened up over time and the contact with the heatsink was poor.

[Jack Crow]

Re: Sansui 5000a blows right channel fuse

Dude,
I went blind with a similar Sansui receiver a great many years back. Like 25 or more years ago.

It came to me with fried outputs.
Went to the parts vendor, got some ECG replacements.
Put them in and pow they blew up.

Pulled the expensive replacements out, tested every dam thing again, what is left looks good.

Repeated the exercise with the same result.

Now I'm getting annoyed.

Third new set of semi's and this time I bring it up on the variac.(Duh).
The amp worked great until I got to the 95 volt input range, then bang.

Made one more trip to the parts vendor, got three more sets of semi.
Took it to a friend who was more skilled. He checked every dam thing just like I did. He put in the parts, and they failed on him too.

Merek had a tool that I lacked.
A proper Tektronix transistor analyzer. He took one of the semis and put it on the analyzer. Guess what the part failed to make spec. ECG had put substandard parts in their bags.

The parts I got could not run at the rated voltage w/o failing.

Merek found some stuff in his lab that would work and the unit went back to his client.

So be careful, check every dam thing, and trust nothing.

Much luck
Jack Crow in VA

[hardwareguy]

Re: Sansui 5000a blows right channel fuse

That's not the first time I've heard tales of woe from NTE/ECG (they became one a while back).

Whenever I can, I will use the original or find a close substitute from a reputable semiconductor firm before resorting to NTE/ECG.

[majid54]

Re: Sansui 5000a blows right channel fuse

Hello
I am a new user I have questions?
I am a Sansui 5000 Mhz problem in burning fuse to the fuse burns if I turn the amps up the field guide course just picture
I am a beginner and do not enter
I thank you for your help
Thanks Majid

[Andrew F. Ali]

Re: Sansui 5000a blows right channel fuse

Not too sure what you are trying to say...Which fuse is burning...and what does 'if I turn the amps up the field guide course just picture' mean??

[majid54]

Re: Sansui 5000a blows right channel fuse

Excuse my language, English is not good
Problem: When I turn on the lamp fuse A burns

[charis]

Re: Sansui 5000a blows right channel fuse

Hi.
This is well know problem on this units and also on BA3000,A-700,1000X,A1100 etc.
Alot of times the relay stuck dont work propertly also the driver transistors are bad.
They use slow 6,7 MHZ transistors and if you change it with a fast ones the sound changes very much losing the warm.
Very dificult to find the same ones.
Also sometimes the TOSHIBA output transistors are pair with another brand and that seems to give problems.
For sure you have to changes all caps and be carefull because you will find a lot of cold joints for sure.
Dont mess with the cables and mark them if you put it out.
Change all the driver trans if need it also make sure that the pcb screws make good contact.
Also i sugest put all the signal cables away from main voltage ones change the main caps from 2000 to 5000 disable high low filter more powerfull diodes disable a b selection speakers new output speaker conections and good cleaning of all switches.You will see another machine..
If you have a schematic please upload it.

[budm]

Re: Sansui 5000a blows right channel fuse

The 5000A is know for bad amp driver boards F-1040, they are replaced with F-6013 boards (used in 5000x).

[majid54]

Re: Sansui 5000a blows right channel fuse

Hello
thanks for your response
You're not my country win 6013
Repair work is not good, if I may, I will send for you to repair amplifier?

I feel used transistor amplifier:
This capacitor is also possible to cut loose than this?