Rebuilding/Upgrading the 2000x

[super98lsc]

Well I completed the 5000x, CA-3000, BA-2000, Now I am rebuilding my office reciever which is an all original 2000x. A friend of mine gave it to me for free when one channel had gone out on him. A quick cleanup and replacing one fuse and its been my office reciever for 2 years.

Issues:

• No FM Stereo Light- Bad bulb
• 2 Lights on the Dial burned out
• Tuner needs a fine tune/alignment
• Right channel has less output in the low end as in noticably less bass output
• Sounds dull overall, especially compared to the modded/upgraded/rebuilt 5000x

I began with the typical, diagnosed the bulbs and FM Stereo indicator,, then Removed the tone control board and removed the 2SC458's & Electrolytic caps. I had all of them new in my parts bin except for 2 which I have to add to the parts order tomorrow.

My plans are to upgrade the unit and do the Baxendall diode upgrade etc.
Few teaser photos for tonight..

 

[petes'picks]

If its half as detailed as the 5000x thread you did this should be useful when I get around to doing mine.

 

[super98lsc]

I will have a lot of detail and photos.

 

[tom3]

Is this diode deal on the driver amp? I have one on the bench right now with a dead channel.

 

[larryderouin]

The "diode deal" is an add-on detailed on this page....... http://conradhoffman.com/Sansui2000x_mods.htm

 

[tom3]

Thanks for the link, several good tips there.

 

[super98lsc]

Box of Mouser parts showed for the weekend! Love having those guys 200 miles away in Dallas. 95% of the time $7.99 FedEx Standard gets the parts here overnight.

Tone control/pre-amp board is done. All new transistors and Elna Silmic-II save for 3 Nichicon Golds in places where Elna did not make the values I needed.

The F-1180 Driver Board was really corroded from the Sansui glue. I removed all that and am doing the updates found on Conrads page + a few other things along the way.

 

[super98lsc]

Few more shots with teh component removed. Time to clean up the board, remove glue residue and prep for new/upgraded parts.

 

[super98lsc]

Driver board completed. Close up of the Baxendall mod, and VBE multipler caps added on the back.

 

[super98lsc]

All biased up and jamming away in the home lab. This little 2000x is impressive. Still have to align and cleanup the FM and swap the output coupling caps tomorrow.
The pre-amp/amp section sound amazing now! Its not even close to the muffled cloudy dead sounding animal I started with. The mods are very very worth while. Thanks to Conrad H for those!!!!

Since I used all my original tranistors including the 2SC281s for the VBE multipliers, but added the 22uf caps across them and did the Baxandall diode upgrades etc, I wasnt certain if the bias control range would be enough. So I tried it first without swapping the 1.5k for 1k on R814/R834 just to see where it would land. Go ahead and change them to 1.0k Ohm per Conrads writeup, if you dont the bias will max at 6mA and that wont fly. Conrad biased his up a bit higher than I have mine at the moment, I plan to add a little umph to it but I am at 14mA for now. Let it play a bit build some heat then I will retest. Dont need any runaways. :nono:

Now I wont cry as much when I mail out the 5000x to Dad tomorrow

Patton Space heater makes a nice 10Ohm load on the high setting for scoping the DC offset.

 

[smurfer77]

Lovely pics and detailed descriptions. Keep it coming.

 

[super98lsc]

After listening last night I noticed one symptom persisted. The left channel was lacking bass. Quick check on the scope proved what I heard.

F-2531 which is the input board hidden under the RF shield by the inputs. Also has the MPX Separation adjustment for the FM Multiplexer on it.
All the signals coming into the amp and pre-drive originate here.
This board had the WORST soldering job I have ever seen in a factory piece of equipment.

I desoldered the entire board, cleaned both sides and am installing new transistors and caps of course. I replaced the 2SC871 with KSC1845FTA. Qty. (4) in case anyone needs it. Moral of the story if your still having issues with a 2000x after recapping most of the unit including the tone control board... dont forget this one.

 

[super98lsc]

Of course as expected problem solved

That board was an ugly mess of cold bubbled solder joints + Sansui death glue.
Channel balance is perfect now. Frequency output per side is spot on even on the scope and to my ears.

ConradH I included a picture of my FM IF strip, mine has the elusive VR203 stuffed and present. It is a muting adjustment presuming working in tandem with the one on the rear panel but I havent put the alignment gear on it yet.

 

[ConradH]

Very cool- glad you had fun with it! Honest to goodness, my 2000x was found upside-down in a mud-puddle at the dump! Works like a champ- all it needed was a little love. I just bought another non-working one because I couldn't pass it up and like working on them. I'll have to see if VR203 is installed.

 

[Hyperion]

The pictures in post #12 are astonishing ! - more blow holes and poisoned joints than you can shake a stick at!

Nice work.

 

[super98lsc]

Thanks guys.
That board was a disaster, I have not ever in my 41 years seen a board like that come out of a factory. I cleaned it 4-5 times with Acetone after removing every single component on it, including the resistors. Even after all that I still had some joints that wanted to turn to Champagne on me.

I think the glue is the culprit. Looking at the board it would appear they used a glue to pre-place the components onto the board so they could then be soldered into place. Well the glue contaminates the board and the component leads. Even my new components were "touchy" to get soldered in without gas bubbles. I went through each hole with a small file/drill bit to clean them out the best I could without lifting/damaging traces. I think baking the board might have been the only other thing I could try to cook out any other contaminants.

I had a few joints like that in the CA-3000 but not to this extreme.

 

[super98lsc]

Chasing down a dim FM Stereo lamp.

• Current supply from the transistor emitter to the bulb is 166mA (spec is 100mA)
• Voltage output from TR407 Emitter to the bulb is 3.45v (slightly more than 1/2 of what specs call for)
• Collector voltage to TR407 from the power supply/ripple filter is spot on at 5.7v
• Bias supply voltage from the multiplexer to the Base of TR407 is spot on at 5.7v test point 4B

Only thing I can think of is TR407 (2sb324) is weak. (Just remember that its a PNP Germanium little 3 wire bugger)
Thinking of this for a sub, unless anyone has a better idea.
http://www.mouser.com/ProductDetail...=sGAEpiMZZMshyDBzk1/Wi8oN7VHZ91OkbvMj7c9d0iY=

I havent pulled it to test or subbed in another just yet.. I have the flu so double checking my brain against this awesome brain trust we have here :yes:

 

[ConradH]

I never realized there were any Ge transistors in there. If you measured the current (more trouble than I would have gone too) and it's high, then it has to be going somewhere. If it's going through the bulb and the voltage is low and the bulb is dim, replace the bulb. That all seems unlikely. Maybe a short in the wiring somewhere? Wrong bulb installed?

Hope the flu is getting better!

 

[super98lsc]

Replaced the bulb already. The other AUX lamps etc are bright and receiving the rated voltage. Not certain I trust the current measurement. Logic says if the bulb is 1/2 as bright and so is the voltage = seems like the transistor is breaking down inside and not providing enough forward voltage to the Emitter. I ordered up those replacements today along with my other pile of common parts I like keeping around. Ill try it and see. Its just annoying when there is ambient light in the room making that bulb difficult to see.

 

[ConradH]

What happens if you take a clip-lead and short the transistor C-E? Does the bulb go to full brightness?