Sansui 1000A wont power up

[Bonsimike]

I purchased a 1000A not long ago at a very good price the guy I got it from picked it up from a estate salvage.
After opening it up I found a failed multicap and numerous others leaking, no surprise its pretty old.

I changed all the multicap's and electrolytic, and most of the PIO caps before I ever attempted to apply power.
connected up my DBT and variac and started to raise the voltage and noticed the bulb was very bright and didn't seem to get any lower.
I checked some voltages on the output of the transformer and I don't seem to be getting any voltage out of the yellow wires (32v?) The front lights do work somewhat but that's about it.

I ohmed out all the output wires on the transformer and nothing seems to be shorted but still not getting the right voltages according to the schematic. I have also checked the diodes and they also seems to be ok even though I haven't replaced them yet.
So now I am stuck thinking I have a bad transformer does anyone have some advice on what I should check next. I can post some pictures also if needed just let me know.

Also like to say Thank you to everyone in the forums for the wealth of knowledge you have put together here.

 

[petehall347]

you might get better replies in the tube section .
first thing comes to mind is the rectifier .

 

[audiobee]

You should have repair the power up problem before the recap..
now there is a big chance that you have made wrong connections on your capacitors...
let me try to walk you through this.
1- check the fuse.
2- check the voltage selector that it is in the 117V position.

if those are ok, now check for AC output on the power transformer.

3- check for 180V AC on the 2 RED wires ?
4- Check for 32V AC on the WHITE wire. ?
5- check for 6.3V AC on the 2 Yellow wires ?
6- check for 6.3V AC on the two black and white wires.?

if all these output are there then your transformer is good.

now while you are in there, check the 2 big tubular resistors ( standing up next to the transformer and next to the voltage selector) .
are they OK ?
- one is 6K (R181).
- one is a combo 6K + 600 OHM ( R179).

these 2 resistors went bad ALL the time.. they are voltage drop power resistors and are working very hard in this sansui design..

I want you to take a close up pictures of under the big can capacitors and post them here so I can spot check for you.

do those steps and report back to here..

 

[Hyperion]

You may be forced to disconnect the 2 red wires (180V AC) and the white wire (32V AC) as described above, to enable you to power up.

 

[larryderouin]

In addition to the very good thoughts by audiobee and Hyperion,What wattage bulb are you using onthe DBT??? And are the voltages shown in your posts on the DBT or wall voltage??? On the DBT, anything less than 150W will result in too much voltage drop, and the unit will show signs of voltage starvation. Plus the lamp will glow brightly all the time. You want the lamp to be able to dim down with no load or very little load. Convert your DBT to be able to handle a 3way bulb (3-way socket, and 3 way bulb.) You can get 50-100-150w 3-way bulbs damn near anywhere. My 1000A will light up a 150w brightly upon switch on and it dims down about 80% by the time it's all warmed up (about 3 minutes or so). A 100W bulb will stay bright all the time with voltages approx 30-50v below nominal. With the 150W bulb dimmed down the voltages are about 10V below nominal.

If the POWER RESISTORS are bad you can replace them as done in this thread. http://audiokarma.org/forums/index.php?threads/1000a-power-resistors.536768/ . I would double check the wiring from the voltage doubler and the 3 and 4 section Filter caps.

Test the tubes for shorts. 6an8's and 7591's especially. Check the wiring from the 3 & 4 section caps and make sure the terminate at the correct point. AND make sure the grounds are secure.

 

[Bonsimike]

Wow you guys are quick with some good information Thank you all very much.

If anyone is wondering why I didn't check the receiver out before I started this project is because when I took the bottom cover off I found all the major power caps and multicaps had already exploded and left white dust everywhere in the bottom of the chassis. I was tempted to turn it on but my common sense won me over and I decided to replace the caps before I toasted something .

When I got home today I went and checked out first my DBT and sure enough it had a 100w bulb in it , Good call larryderouin I guess I left it in there while testing my SX1250 either way I switched it to a 150w. I fired it up and the power came up and the bulb went dim what a relief. I started to look at the voltage as described in audiobees instructions and they still seemed low so I started to pop out tubes and sure enough there are a bunch of shorted ones.
So now that part is figured out the voltages I measured are below.

Red wires 180.9V AC
White,White 31.9V AC
Yellow,Yellow 6.4V AC
Green,White 6.4V AC
Blue,Black 6.4V AC
I ran it for about 45 min while I was measuring things and it seemed pretty stable but then again most of the load from the tubes was not in place.

I have also checked the giant power resistors and they are ok for the moment but I have already purchased new omite replacements for all of them and hopefully I can mount them onto a heat sink to help dissipate some heat. I have also started the 4 bias pot upgrade since mine only has one pot ATM.
So I have a brand new set of tung sol 7591A tubes that I am deathly afraid of putting in right now but I also need a couple 6AU6 and 6BA6 tubes. I would imagine they are not going to be to easy to find I hate going thru Ebay for NOS its more like POS usually.

Is there is anything else I need to check before I plug in some new/working tubes ?

Thanks everyone again I will keep my progress updated shortly and add some photos when I get this cleaned up a bit.

 

[larryderouin]

Those caps look like mine did when I opened it up. It hadn't run in 15 years. Replace EVERY ONE OF the SUZUKI PIO's with equivalent FILM caps. And all the electrolytics. I have 2 Fisher 800c's and the 1000A blows them out of the water wattage wise. It's a bit more brash, but the FISHER's are easier to listen to when tired. Less listener fatigue.

http://www.abcvacuumtubes.com/ I get all my small signal tubes here. Very reasonable. 6au6 and 6BA6 are about $3-4 each. New old stock. I've never gotten a used tube from them either. And you can specify your brand (up to a point.) I use GE tubes in the 6AU6, 6BE6, and 6BA6 spots (all the tuner tubes). The 6AQ8's are $15 each and there are 3 in it. 6DT8's are good sub's for the 6AQ8 and cost $3.00ea. Mine doesn't like the 6DT8 in the Multiplex unit so use a 6AQ8 there. The 6AN8's I use are Sylvania's from Jim McShane (I think paid $9.00 each for the years ago before i knew about ABC) it had Matsushita's and they were toasted. The Sylvania's have lasted almost 10 years now.

ABCTube prices
6AU6 $4.00
6BA6 $4.00
6BE6 $3.00
12AX7 $10.00 (EI)
6AN8 $7.00
6DT8 $3.00 Sub for 6AQ8
6AQ8 $15.00

The 6AN8's tend to get run hard as drivers. With those tube numbers you can specifiy what you'd like (provided they have that brand in stock) except for the 12ax7's. The EI's are pretty good tubes (These are your phono tubes) Otherwise GE's for the 6AU6's, 6BA6's and 6BE6, GE/Sylvania for the 6AQ8 or 6DT8 and the 6AN8's. If the tuner works fairly well, installing new tubes shouldn't bother it.

 

[audiobee]

Slow down, you are jumping too fast here.
try to get the unit up to to fully running condition first before attempt any "mod" on it.

 

[Bonsimike]

Yep I just ordered a bunch of tubes to get it running completely first they should be here is a couple days. I am not going to do anything till then except to clean some of the old dust and oil off the chassis. also ordered the remainder of the caps I missed. I love the look of the front panel on this with the old style lights I need to find a couple more I am not going to put LED lights in this it just wouldn't look right to me.
I also have a 500A that is in mint shape I am going to start on after this that will be in another thread.

 

[larryderouin]

Updates?????

 

[Bonsimike]

Ok sorry for the delayed reply been real busy at work. I finally received the rest of the caps and a new set of TS tubes and NOS tubes for the rest of them. I finished replacing all of the PIO caps and electrolytic almost every one of them were out of spec or the electrolytic were mostly dead and leaking.
After I went thru and checked all my work I powered up the receiver with the aid of the variac set to 115v. I let it warm up for a few min then checked the voltages against the schematic and they seem to be very close or right on the money.
I turned up the volume a bit and noticed I am only getting sound out of one speaker the right side and the left side is very low. I have already cleaned all the controls with deoxit they were pretty gummed up with god knows what someone sprayed on it last time. Not really sure what direction to head next. I do have a Tektronix 475 scope maybe I should try to trace the signal? any advice would be greatly appreciated.
Almost forgot I have also connected an Ipod to the aux port and the same results. and I have also swapped tubes around (left to right) and same results only sound on the right side.

 

[audiobee]

"Slow down, you are jumping too fast here.
try to get the unit up to to fully running condition first before attempt any "mod" on it."

just like I have warned you from the previous post... you should have tested the unit before doing any recap.

now your first task is to tell us whether the "single" channel operation was the original problem of the virgin receiver or it was cause by "your" recap mistake.. ??

 

[larryderouin]

Audio. I don't see where Bonsimike is jumping way ahead of himself here. He got a Sansui 1000A in typical worn out condition, got underneath and checked the condition of all the caps (of which the majority were blown or leaking) replaced them, and retubed it. At this point he has Good sound in one side and low output in the other. I see or have read of absolutely no "MODS" done to it yet. Just an honest attempt to resurrect a 50 year old receiver. He's done pretty much everything needed to get it to this point without any "MODS" that I've read about. I consider the 4 pot version an UPGRADE especially with NEW STOCK Russian Tubes. Also the Large Power Resistors run exceedingly hot and I've seen more than one set that was on the verge of crumbling. I consider that replacing them is NOT a MOD, but a modern upgrade. He needs help, NOT continued berating about ""mods". Maybe you read more into it than I have (as I also have a 1000A and brought it back from the edge of the precipice as my 1st receiver and it's still running fine). These units need an almost total replacement of any and all caps, except for the very few and far between films, to be able to start up 1/2 way normally without major problems. These units also run most all of the tubes very hard. So I gave him info on what and where to get them IF NEEDED. Apparently he needed more than the outputs and the drivers.

Bonsimike. Do the pots and the switches (all of them) again. Exercise the heck out of them after spraying them. Use faderlube after the DeOxit. And exercise them again. Clean the tube sockets with a Dental Braces brush and DeOxit. If you don't have any, use an old tube. Also check that the heaters on all tubes are working at the specified voltages. See what happens now.

 

[audiobee]

sorry for the misunderstanding.. when I said "mods" I also mean "recaps".

 

[Bonsimike]

Ok I will do that again and check the voltages and report back shortly.
Just for the record I have not modified anything yet I would rather just get this thing working first.

 

[audiobee]

Ok I will do that again and check the voltages and report back shortly.
Just for the record I have not modified anything yet I would rather just get this thing working first.

that my point.. but it is too late now.
now go back and recheck your recaps work.. make sure you made all the correct caps CONNECTIONS and bad "new" capacitors made it to the end users all the time too.
do that first then come back here.

 

[Sam Cogley]

sorry for the misunderstanding.. when I said "mods" I also mean "recaps".

Your definition of "mods" is wrong.

 

[Bonsimike]

Spent a couple of hours last night cleaning the controls and removed all of the tubes and cleaned and retention the sockets that needed it. the cleaning of the controls seemed to help the scratchy sound as you turn them, that is gone completely now but still only sound out of one side.
The odd thing I found when I was flipping switches is the stereo NORM and REV don't seem to work right to me. If you flip it to stereo REV I get sound out of the other side that does not normally produce sound (left side) and I flip it back to stereo NORM and the right side comes on and left side goes low. I guess the one good thing that came out of this is the left side will produce sound thru the output transformer I was getting nervous that it may be bad.

I am not sure on the operation of this switch since I have never owed one of these but I would guess it should not work like it is. shouldn't it just make the left sound come out the right side and right come out the left? Going to try cleaning the rotary switches with a small brush or something to get the rest of the black stuff out not sure if it will do anything but I guess it wont hurt

 

[Bonsimike]

After taking the front panel off so I could get at the rocker switches I finally found the issue. I went down the line and sprayed some of the cheaper deoxite spray into each one and found it was the Tape Mon switch. I cleaned every one of them and I am going to go back thru them again clean them before I add some fader lube.

While I have the front panel off I am going to clean everything up BUT I wasn't sure about the glass with all the old silk screening what is the best method to clean that off? its in really nice condition so I don't want to mess it up.

I am not done with this thing yet and have a bunch more questions where to go next and Thanks to all for the advice its been interesting do far.

 

[audiobee]

"After taking the front panel off so I could get at the rocker switches I finally found the issue"

so you found and fix the single channel issue and both channels are playing now ?

"The odd thing I found when I was flipping switches is the stereo NORM and REV don't seem to work right to me. If you flip it to stereo REV I get sound out of the other side that does not normally produce sound (left side) and I flip it back to stereo NORM and the right side comes on and left side goes low."

good news here. this prove that your other "dead" channel is working... the problem is dirty "controls and switches"
NORM = Normal, as connected
Rev = reverse, output is flip from left to right...

also to tighten all the rotary controls to the chassis with a socket wrench.
the best way to clean the dial glass is with a damp paper. Don't use any cleaning chemicals or you will run the risk of removing the lettering too.

there are 2 slide switches on the batch of the unit that need a "really" good cleaning.
- Impedance switch
- Phase switch..
use dioxide and slide them back and fort while cleaning them..

I can send you a pdf copy of the user manual.. let me know.