Rebuilding/Upgrading the 2000x

Sorry should have mentioned that last night, it gets full bright as it should. That was the first test I did before measuring the bias coming off the MPX board. My only thought was well what if its not getting enough bias current.
 

Attachments

  • IMG_3846.jpg
    IMG_3846.jpg
    52.8 KB · Views: 40
  • IMG_3845.jpg
    IMG_3845.jpg
    53.4 KB · Views: 38
Pretty much has to be the transistor. I'd try replacing it with some generic silicon device unless there's some reason Ge worked better.
 
I went through my new stash of PNPs and found a bag of BC327BUs
Soldered one in, provides 5v to the lamp and it looks great.

Spec calls for 6v max but no reason to run it any hotter than that.
Problem solved.
I tested a more robust KSA916YTA but it wanted more bias than the MPX is designed to give to get above 3.87 volts out. The BC327 provides 5.05v which is great.
Its Collector current is .800mA vs the factory 1mA close enough.

Cleaned up distortion with a quick alignment on the discriminator. Sounds great stations on center, pulls in on 4-5 on all of them with ease. Think I will call this one done.
 
Last edited:
Finished it all up back in the case and on the shelf. Sounds great on its own, however I am also playing with the BA-2000 I just rebuilt a few weeks back so the 2000x is serving tuner/preamp duty quite nicely. Aligned the FM cleaned up the interior of it and finished the ripple filter/rectifier recap this afternoon.
 

Attachments

  • IMG_3861.jpg
    IMG_3861.jpg
    53.3 KB · Views: 37
I listened for a while last night and it just sounded bright/sibilant to me. I slept on it then got up and pulled it back apart this morning.

When I rebuilt the F-2531 board I replaced the 4 2SC871s with KSC1845-FTA. BAD MOVE!!! The gain curve on the KSC1845-FTA isnt even close to the 871s. I couldnt think for the life of me why this amp just sounded sibilant excessively revealing. It was clean and clear but just not something you would enjoy and could kill dogs from 6000 yards out. Backing off the tone controls didnt help and adding bass just pumped up the mud factor.

I pulled the 1845s and gain checked them on the HFE tester = 206
Cleaned and checked the 871s = 804-801 across the 4

Re-installed the 871s and it has its Sansui sonic signature back and the low end is nice deep and warm. Tone controls are flat and its perfection!

So now... I get to open my CA-3000 back up and remove all the damned KSC1845-FTA subs I used in place of its 871s :gigglemad
Thinking of 2N4401 for subs there.. feedback anyone?
All part of the learning process I am just glad I have enough brains to figure this stuff out.:scratch2:
 
Last edited:
Now that it sounds good lets see if I can properly align the FM properly enough with the gear I have. Leader LSW-333, Heathkit IG-37 Stereo Generator, and the trusty Tektronix 2246 Scope.

10.7 IF Sweep fed into TP101 per service manual.
Scope connected to TP201 on the IF Strip

Take all the help I can get here guys as this is only my 3rd time doing an alignment. :tears:
 

Attachments

  • IMG_3865.jpg
    IMG_3865.jpg
    71 KB · Views: 22
  • IMG_3866.jpg
    IMG_3866.jpg
    90.2 KB · Views: 21
  • IMG_3867.jpg
    IMG_3867.jpg
    88.9 KB · Views: 21
Well I got the leader locked in on 10.7Mhz fed that singal in and peaked out the transformers and adjusted the waveforms. No issues until I got to 3rd transformer and found one of the slugs was broken already. Guess someone already "worked" on this in the past. (I got this unit from a friend for free years back) Anyhow I tried to gently coax that one into alignment but wasnt going to happen if I wanted peak signal etc. Waveforms looked ok but I was losing most of the amplitude in that 3rd stage.

Now the question is where to find a replacement slug?
I dont use the AM should I rob one for now from it.. hate doing that sort of thing. :no: Bummed.
 

Attachments

  • IMG_3875.jpg
    IMG_3875.jpg
    43 KB · Views: 24
  • TP202.jpg
    TP202.jpg
    61.6 KB · Views: 17
  • TP201.jpg
    TP201.jpg
    72.2 KB · Views: 17
  • Discriminator.jpg
    Discriminator.jpg
    70.3 KB · Views: 18
Meh, I stole 2 slugs from the AM section for now.

Works great now that it doesnt have 2 slugs and fragments all hanging out inside the transformers. I couldnt get a decent waveform off the 2nd transformer either, so after screwing with it for a bit I thought why not just back this top slug out and have a look.. bottom corner was busted off that one too laying inside the transformer getting sandwiched around between the bottom and top slugs. Waveform had this nasty juant in it that wouldnt clear out. Popped in another slug and lined up in about 30 seconds. Sounds great now grabs all stations on a 4-5 signal and no more distortion in the sound.
 

Attachments

  • IMG_3879.jpg
    IMG_3879.jpg
    55.7 KB · Views: 17
Super981, I've been following your restoration, very informative stuff, great pics as well, thanks for sharing. I also have a 2000x, did a little bit of resto, recapped the preamp board, redid all solder connections, as mine looked like yours, glad I left the 871's alone, replaced the 458's on the tone board, but no caps, didn't touch the amp board. Have most of the parts, just kind if lost my nerve, when my issue of weak rt channel seemed resolved. My fm board also has the same crap solder job, and I'm pretty sure I need a realignment, but I'll have to get someone for that.
 
Not sure what size the slugs are but http://www.electrojumble.org/passives_013.htm has a few. Also https://www.surplussales.com/Inductors/Ind-SlugTu/Ind-SlugTu-6.html if you scroll down a bit. Another trick might be to epoxy a short plastic rod to a broken slug to act as a handle, if not too much is missing.

Cool thanks Ill do that to fix the AM, I robbed the studs from there for now and the FM is locked in beautifully now. Someone had really busted up the 2nd &3rd IF transformers inside.
I can say that if all the pieces aren not uniform (sections missing on the slug for example) then good luck getting a nice waveform. :no:

I mic'd the slugs they are: 6mm long x 4.60mm diameter.
L470 4.5mm x 8mm long should work for the Sansui stuff to be spot on it might be worth while to grind 2mm off one end very carefully.
The factory coils/transformers are Toko as well.
 
Last edited:
I took a look at Alltransistors.com Just to keep it simple, I stayed with transistors I'm somewhat familiar with.

Looked at the spec's for the 871, 1845 and 1815. I'm thinking the 1815 would be a closer match to the 871 than the 1845. Note that the hFe ratings are minimums, there were no Maximum hFe ratings.


attachment.php



I've got a bunch of ksc1815's and a 2000, 2000A, and 2000x all with 1845's in the phono sections. I can replace one with 1815's and compare to the others.

Larry
 

Attachments

  • ScreenHunter_153 Feb. 16 00.17.jpg
    ScreenHunter_153 Feb. 16 00.17.jpg
    36 KB · Views: 61
Supposedly the ksc1845-FTA has less gain than the previous non FTA. However that one isn't available anymore.
 
Larry,
I added 100 KSC1815s to my Mouser order tonight. I am tempted to try them in place of the 2SC871 on one channel of the 2000x then feed it a mono audio signal and some test tones and see what shows on the scope as well as the ears.
 
Let us know how that turns out. Been busy with tweaking and fixing my 2 800-C's.
 
Will do... I may order a little curve tracer today just to add to the pile of toys in the lab. In a way I think specs are a bit like aligning a car chassis, the numbers are good guidelines but you have to test drive it and make small adjustments until it feels right. Audio seems to be the same way.

Capacitors- I have noticed when I test caps on the LCR that capacitance on the Nichicon caps is usually lower than spec and the ELNA Silmic-II are nearly spot on ever time. The ELNA also appear to test more accurately at different sampling frequencies where the Nichicons also have more variance, lower capacitance etc. So it does make sense to me that brand/series of cap could affect sound. Not every cap value is available via Mouser in ELNA. I have begun to stick to them now wherever possible.
 
Resurrecting this thread as was about to start replacing the 2SC458LG's on my 2000x with ksc1815FTA's. Then I saw this and decided not to. I noticed on Mouser they have 1815's with a YTA suffix. Anyone know if these would be better or what the ideal available replacement transistors are?
 
Bolan; Hope you meant KSC1845FTA. The KSC1845FTA is fine for replacing the 2sc458 in any flavor. The suffix on the transistors is 1st letter is Gain (hFe) the next 2 are packaging BU= Bulk T, TA, etc are taped (think 30cal ammo for a 1919A4 machine gun) for use in a machine. The 2sc871 is not known for being noisy and susceptible to breakdown like the 2sc458. 1845FTA is a low noise unit, where the 1815 is not a low noise unit. The 1815 is also a lower power transistor than the 1845. The avg hFe for the 1845FTA is approx 300 from what I've tested, and the avg hFe for the 1815Yta is about 200 avg. The Datasheets for each are on the mouser page with the particular transistor. Installing the 1815 will result in a lower amplification of the Phono board or the tone board. The 1845 I've used in my 2000,2000A, & 2000X as long as 9 years now (the 2000A) with no problems.
 
Yes, I confused the numbers, I indeed ordered and planned on using KSC1845 - FTA's to replace the 2sc458's (2 on the driver board and 6 on the tone board) - I misread super98lsc's comments on replacing the 4 2SC871's on the F-2531 board. Anyhow, you answered my concern that the FTA meant it would not be enough Gain, thanks! I'll replace them tonight - hopefully this will get rid of the hiss in the left channel.



Bolan; Hope you meant KSC1845FTA. The KSC1845FTA is fine for replacing the 2sc458 in any flavor. The suffix on the transistors is 1st letter is Gain (hFe) the next 2 are packaging BU= Bulk T, TA, etc are taped (think 30cal ammo for a 1919A4 machine gun) for use in a machine. The 2sc871 is not known for being noisy and susceptible to breakdown like the 2sc458. 1845FTA is a low noise unit, where the 1815 is not a low noise unit. The 1815 is also a lower power transistor than the 1845. The avg hFe for the 1845FTA is approx 300 from what I've tested, and the avg hFe for the 1815Yta is about 200 avg. The Datasheets for each are on the mouser page with the particular transistor. Installing the 1815 will result in a lower amplification of the Phono board or the tone board. The 1845 I've used in my 2000,2000A, & 2000X as long as 9 years now (the 2000A) with no problems.
 
Back
Top Bottom