Discussion in 'Exclusively Sansui' started by Bigdrive, Aug 5, 2017.
wonder what he's been doing?
Yes, he's been a bit quiet lately, last I heard he was making the replacement Phono Motherboard and considering installing one.
Thanks, the parts are on order, or should I say the 3rd and 4th wave of parts as I am trying to one board at a time and test. that's not possible right now as I am trying to complete driver boards before firing it up again....no pun intended.
I do have a question about the driver board. Mine does not have a resister or wire on the solder side of the driver board as depicted from the picture ( borrowed from amp8.com) I think its a 22k resistor and what looks like lamp cord. I believe this driver board is upgraded as it has the 47pf on c15 and c16 instead of the 33pf the SM calls for. My interpolation from some posts is that another 22pf be added to those positions for better stability. I am going to replace them with 47pf for now unless the gurus advise otherwise.
I have supplied a pic of my board and circled what I see from pics of amp8.
Please advise if I should add resistor and/or lamp cord and if so what value is resistor?
Any advise is welcome, cheers
This might help, it's one of my driver assemblies, (before any work).
I am not sure whether you should add the additional wiring and components. That looks like a 2.2K resistor (not 22K) as seen in the top of the pictures of our respective driver boards.
The X1 I worked on had 47p instead of 33p in those positions, if it looks factory, put in what was already in there, many service updates were not documented....
There are two resistors on each driver board that need replacing, they are fusible type and drift in value, I'll look it up and post unless John can remember where they are....
As I recall the 47pf is an upgrade and correct, the 2 resistors on the driver boards are 390 ohm, R36 & R37 - they drift very badly, 'open cct' and '211K' were what two of mine read.
Yes these 47pf are correct. Also make sure to reflow all solder points.
An important aspect of these boards is to make sure that you have the ground cable to the star ground to chassis connection as a solid connection. This star ground to chassis connection is located on the phono motherboard.
Since you have an earlier version also apply the additional ground to the flat amp pcb ( see my post on this). When you test the amp take out the phono mm and mc boards and make sure all is running well in the amp
Then work on the mm and mc boards, including the modifications required on the phono motherboard ( if this was not yet done). Also the phono motherboard gets a grounding update same as for the flat amp, this was one of the factory mods to improve stability. This was later integrated into the newer versions of this board. Please post some pictures of the phono mother board underside
Ohh yes don't rush, mine just took 6 months to restore It is Well worth the effort. I listen to it almost every day and it keeps surprising me.
If you do not want to use the phono of the amp, you can leave the boards out. Otherwise also resort the powersupply to the phono boards and the flat amp to the last detail. The phono boards run in class A and get hotter than the power amp.
Upon initial check all resistors were good but r102, r104 r30 and one of the output transistors 4.7 ohms have drifted on the driver board. I have rechecked r36 and 37 and both are within spec and look ok. Thanks for the heads up. Wish I knew whether to add that 2.2k though. I guess really what I want to know is "did someone else forget to put it on"
I will be honest, when I bought the amp I had already done a lot of reading on it and thought with support I could recap it provided it worked when I got it. I had just finished my Kenwood KA-1000 to 90% complete and was not happy with the sound. After thinking about it I decided NOT to recap or anything and run it until its next hissy fit. The reason was that I thought I would do more harm than good to a amp I have the utmost respect for. I did some more reading and since the MM was not working up to snuff I would recap and check it and down the rabbit hole I went. I know some of these subjects are/where hotly debated and I am not saying anything here to start up anything just to let you know I want to listen to this amp and enjoy it not to change everything and be unhappy that I ever touched it.
I do know one thing, I love the way this amp sounds now.
Ahhh Harolda, I drool when I look at your amp. 6 months! That is not going to agree with my type A personality, but I love the end of your story and that's really what I want. Will do on the testing and grounding procedures thanks.
Here are the pics of the underside of phono MB. The only thing I have done is replace two top caps. I have not really looked at it or measured anything yet. Sorry had to do two shots.
Update and more info needed.
All caps including black flags replaced. All glue and corroded resistors replaced. All resistors checked for value and replaced if required. R36 and R37 not replaced right now but i have them here. Many transistors checked but not all.
My intention was to get the caps out then fire it back up, check both my work, how it sounds and to get some voltage numbers from it before going into phase 2.
It fired up last night! I left the mm amd equalization boards out as instructed and then instead of working on it til 2am, listened to it until 2am. Its only the second time i have heard it and WOW it never failed to impress. Sound imagining and stage was incredible. I ran cd's through it and was perfect. I ran mps through it and the ones i know that are well done sounded good but the regular ones sounded bad, which is good. the amp was able to show bad in, bad out.
Once i get some numbers and if they are good, the phono boards will go in, so i can see how they are. Then the unit will be completely disassembled again to get grounding mods and the variable resistors replaced. Also the speaker terminals replaced. I will be using the amp to listen to vinyle and my R2R.
Now for the questions/conformations,
With phono and equalizer boards out, flat amp adjusted first? meter connected to tp1 and ground then tp2 and ground adjust as required?
Then driver board? for the 0 volts do the speakers remain connected? and meter connected to both speaker posts? For bias exactly as in manual picture, between pins 19 and 20 i think on the little 3 pin connector, adjust as required.
Phono boards go in and for equalizer board between tp1 and ground on both boards, adjust as required then mm tp1 to ground on both boards, adjust as required.
Let me know what you think and correct me as required. Any tips and precautions other than dont get myself electricuted, is always welcome.
My sister has several au717's and the volume know has a detent click for each line on the faceplate, does the aux1 have that or not? Mine is not doing that and i am wondering if its normal.
Kevzep, I was looking at your resent aux1 repair and was wondering generally speaking what kind of caps did you use? and why? I used mostly FG's and some silmic 2's. Its more of a general question as my choices were based on size than anything else. I also would consider changing some again if there a question of i did not put in the right flavour in certain parts of the amp.
I used Panasonic FC and FM, I like the results and size options, they are good caps, I'm not particularly into the witchcraft of Caps...
Looks like you also used good caps....
The sound is in the design not the caps, so carry on......
Thanks, this is indeed a first generation amp. It has the factory modded phono board with the grounding update. The later generation board has all these mods incorporated.
If you want to use by il, then restore the mm and mc boards. Also replace the small relays!
Yes, I will be using the phono mm section. It sounds excellent. The left channel still has a problem on phono 1 or 2 unless I HIT it hard on the side then everything works perfect.
The phone boards are recapped and waiting for the order to come in with trimmer pots to replace.
I have adjusted all of the amp, but have the infamous "unable to get -10.5 volts from trimmer" it runs out of adjustment. It's also waiting on that shipment for the grounding capacitors mod.
Here are some pictures so far
Hyperion has been helping me with the trimming issue, thanks John
What's best to clean and lub contacts?
Best thing to do is to completely disassemble the switches ( take lot of pictures). Then use deoxit on normal paper to clean the inside of the sliders and the pins. The paper works as an vey mild abrasive and you can see the dirt comming off.
Lube with deoxit gold before assembly
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