Component replacement challange, informed upgrades to an Sx, paging Leestereo

[cwh]

That cheat sheet HAS to be model specific for capacitance INCREASES. Replacing with like values is no problem.
remember, old e-caps used to be -20% +80% tolerance - todays can (check the data sheets) be a lot tighter spec.

interesting news about the green mylars.on the tone boards.

MTF, for the SX780. What resistors would you improve given a better modern replacement exists?

Carl

 

[cwh]

I look at the totl designs from many mfgs and compare them to say a 780, you can see where they did a better design and components since they had more $ to play with

Hey, yeah that's something I've been doing and your comment reflects what I'm driving at. My OP involves me basically looking through a tech who's looking at the designs and improving...When I'm in a position to make those executive decisions I'll make em and hopefully post my work and inspire someone else to learn.

The online access to schematics is amazing. Thank you HiFi engine! And thank you Canada! Gotten some helpful guidance your audio techs. Dualcan over on vinyl engine gave me a bunch of it for a Dual 1015 project in progress. Anyways...

Of course if you can use a film over a ecap, you are better off in general. you know how it goes as far a quality, mylar,polyester rolled,polyester stacked,... polyprop, teflon, polystyrene.

I don't get anxious using 5% Wima or Kemet poly stacked films for blocking. I'm sure the 10% is still a huge improvement given what they replace but oh well.

 

[larryderouin]

Mostly noisy crackling and popping in the tone circuits, and one Sansui they were leaky and over 25% out of tolerance. They were generally the last items replaced after the usual, caps, resistors, semi's replaced with no relief.

I saw early on where it was being developed in to housing. Sentimentally as my mother was stationed in the old hospital in the 50's, I was born there in '55, and then 19 years later stationed there, I wish the Navy had turned it over with the proviso that it continue as a hospital. But that wasn't in the cards. Very saddened to hear it was torn down.

 

[markthefixer]

Resistors IMPROVE??? As in changing the resistance value? NONE. BIG NO-NO

Changing resistor types? yes sometimes- it's rare.
Increasing wattage - only VERY carefully - some are INTENDED to pop on faults for safety's sake (marked with a triangle in Pioneer schematics and Pioneer BOM's)

only with careful, thoughtful reverse engineering analysis.

some low resistance value resistors that could have been stressed (damaged but not out of spec) are preemptively replaced.
Again, reverse engineering tells which.

 

[moewillis]

The team at Pioneer knew what they were doing

 

[cwh]

Resistors IMPROVE??? As in changing the resistance value? NONE. BIG NO-NO

Changing resistor types? yes sometimes- it's rare.
Increasing wattage - only VERY carefully - some are INTENDED to pop on faults for safety's sake (marked with a triangle in Pioneer schematics and Pioneer BOM's)

only with careful, thoughtful reverse engineering analysis.

some low resistance value resistors that could have been stressed (damaged but not out of spec) are preemptively replaced.
Again, reverse engineering tells which.

Nope I'm certainly not interested in changing values. Is that really something people ask about?

Yes types.

Referring back to my post #13, if I had an SX-780 bare board and a bag of NOS SX-780 components... and I'll also add to that, a bag of new resistors of every flavor and value...

Would Mark the Fixer stick with the old bag or would he make a few subs and grab from the new bag?

Please read:

I'm not trying to re-engineer this based on wild notions and delusions of grandeur. This otherwise nice receiver was thrown out with a shorted STK. I'm fixing it and saving it from the landfill. I'd like leave it in a better place than I found it so it will live a long musical life. If can solder in a component that differs from the plan but adds value then I'd like to do it.

This why I'm asking technical questions about upgrades.

 

[cwh]

Mostly noisy crackling and popping in the tone circuits, and one Sansui they were leaky and over 25% out of tolerance. They were generally the last items replaced after the usual, caps, resistors, semi's replaced with no relief.

I saw early on where it was being developed in to housing. Sentimentally as my mother was stationed in the old hospital in the 50's, I was born there in '55, and then 19 years later stationed there, I wish the Navy had turned it over with the proviso that it continue as a hospital. But that wasn't in the cards. Very saddened to hear it was torn down.

Thanks for putting the green mylar info out. My Sansui 2000 is still making a little crackle after complete overhaul. Another guy is a facing a similar situation so I'll post this.

Well I hope they do in fact do save this last historic piece of Oak Knoll.
http://www.eastbaytimes.com/2016/11/26/oak-knoll-clubhouse-is-spared-from-wrecking-ball/

 

[leesonic]

Referring back to my post #13, if I had an SX-780 bare board and a bag of NOS SX-780 components... and I'll also add to that, a bag of new resistors of every flavor and value...

I had an SX-626 receiver that the power amp board had so many bad components and duck-taped wires inside, I took everything off the board, cleaned it, and fitted all new components. That thing sounded sweet! I say go for it if you have the time.

http://audiokarma.org/forums/index....p-board-caps-transistors-and-trimmers.459128/

Lee.

 

[moewillis]

So you are asking if there has been any advancements in electrical components over the last 40 years? Yes, virtually every component is superior to what it once was.

Stripping boards and fully repopulating is a HUGE task and will put you firmly upside down (from a parts/labor standpoint) on an sx-780.

 

[zebulon1]

Not worth it.

 

[rcs16]

I don't get anxious using 5% Wima or Kemet poly stacked films for blocking.

An important point is that they will last for near ever, vs your cheaper alternative in which are being replacing due to expiry.
imo putting in the new stk modules would be the biggest bang for the buck on a 780 as already witnessed. But then again many do not need/want that extra expense vs reward. To each there own.

Would Mark the Fixer stick with the old bag or would he make a few subs and grab from the new bag?

It is an economic/time issue, technically of course it would be better to use new parts unless they do not have the same characteristics as the old ones, i.e 2sk30 njfet.

 

[Caughtthebug]

I agree with rcs16. My 780 was already recap.and I thought it sounded awesome. But I keep blowing the stk's. The last time it took a lot more with them. Well worth the investment. A big improvement. I even have 2extra boards I can send you.

 

[cwh]

So you are asking if there has been any advancements in electrical components over the last 40 years? Yes, virtually every component is superior to what it once was.

Stripping boards and fully repopulating is a HUGE task and will put you firmly upside down (from a parts/labor standpoint) on an sx-780.

Nope, I'm was asking if there are any less than ideal resistors that could use an update, from MTF's point of mind.

 

[moewillis]

Nope, I'm was asking if there are any less than ideal resistors that could use an update, from MTF's point of mind.

in the 780 or in general?

 

[moewillis]

So any suggestions AKers on key areas that you always improve upon in a Pioneer, or in vintage amp circuits in general?

-Carl

Hey guys thanks for the replies but the nature of the my post was completely lost in translation. I'm very familiar with most the content on AK, both read and applied.

I was asking if professional or seasoned audio repair people have certain components (certain stages) that they always upgrade when rebuilding.

I would assume that there probably is some room to improve an amplifier's circuit through changes in components.

I'm hoping (early Boxing Day gift?) that you might offer a cheat sheet for a freshman fixer. A sort of generalized paint by numbers approach towards updating circuits. Your rebuild threads have forwarded my of learning much more quickly than text books. I'd actually like to find a Marantz to follow along with. I will say I'm ok with being a ways off from the theory of F values and subbing smaller value films for filtering. Also RIAA circuit manipulation.

Carl

MTF, for the SX780. What resistors would you improve given a better modern replacement exists?

Carl

My OP involves me basically looking through a tech who's looking at the designs and improving...When I'm in a position to make those executive decisions I'll make em and hopefully post my work and inspire someone else to learn.

Nope I'm certainly not interested in changing values. Is that really something people ask about?

Yes types.

Referring back to my post #13, if I had an SX-780 bare board and a bag of NOS SX-780 components... and I'll also add to that, a bag of new resistors of every flavor and value...

Would Mark the Fixer stick with the old bag or would he make a few subs and grab from the new bag?

Please read:

I'm not trying to re-engineer this based on wild notions and delusions of grandeur. This otherwise nice receiver was thrown out with a shorted STK. I'm fixing it and saving it from the landfill. I'd like leave it in a better place than I found it so it will live a long musical life. If can solder in a component that differs from the plan but adds value then I'd like to do it.

This why I'm asking technical questions about upgrades.

Nope, I'm was asking if there are any less than ideal resistors that could use an update, from MTF's point of mind.

im confused about what it is you are really after here.

 

[cwh]

I had an SX-626 receiver that the power amp board had so many bad components and duck-taped wires inside, I took everything off the board, cleaned it, and fitted all new components. That thing sounded sweet! I say go for it if you have the time.

http://audiokarma.org/forums/index....p-board-caps-transistors-and-trimmers.459128/

Lee.

Hey "other" Lee. Yeah man I like reading through your builds, cool stuff.

Somehow my posts are being misunderstood or at least skimmed over with assumptions. Whatever though, it's all good in the hood.

The 780 is clean and completely effing with every part isn't necessary.

This KA7100 though...haven't opened it up but I expect a tear down. I believe you know something about these guys. How's the triac working out?

 

[cwh]

I agree with rcs16. My 780 was already recap.and I thought it sounded awesome. But I keep blowing the stk's. The last time it took a lot more with them. Well worth the investment. A big improvement. I even have 2extra boards I can send you.

Hey thanks for the offer, that's very cool. I know of another dead 780 and it's safe to assume one of it's STKs is blown. If I make it out of this thread alive I might become a fan of Pioneers. Actually never listened to any SX, SA etc...but I also have a trash picked 980 and 3700.

I'll shoot you a PM
-Carl

 

[moewillis]

Somehow my posts are being misunderstood or at least skimmed over with assumptions. Whatever though, it's all good in the hood.

If I make it out of this thread alive I might become a fan of Pioneers.
-Carl

i dont think this is quite a "make it out alive" sort of situation. i cant speak for everyone here but i am merely trying to figure out how to help assist you. you have touched on a capacitor change, improving an amplifier's circuit, a cheat sheet for generalized amplifier modification, bags of old and new components, resistor changes, sx-780 mods, generalized mods and then following it up by saying you want all of this without redesign or component value changes.

im not being a dick im just trying to sort it out here. you have the attention of some of the smartest people on this site (not saying i am because im not). if they can help they will but they have to know what you want...

 

[cwh]

i dont think this is quite a "make it out alive" sort of situation. i cant speak for everyone here but i am merely trying to figure out how to help assist you. you have touched on a capacitor change, improving an amplifier's circuit, a cheat sheet for generalized amplifier modification, bags of old and new components, resistor changes, sx-780 mods, generalized mods and then following it up by saying you want all of this without redesign or component value changes.

im not being a dick im just trying to sort it out here. you have the attention of some of the smartest people on this site (not saying i am because im not). if they can help they will but they have to know what you want...

Hey man I appreciate that and I'm not trying to be passive aggressive. What I'm after here are opinions on a few key areas on a 780 that could use a preemptive update or upgrade beyond the usual stuff. Not after changing everything.

I cited Leestereo's rebuilds as an example as he doesn't just change out everything but also doesn't just do the standard recap.

 

[leesonic]

Hey "other" Lee. Yeah man I like reading through your builds, cool stuff.

Somehow my posts are being misunderstood or at least skimmed over with assumptions. Whatever though, it's all good in the hood.

The 780 is clean and completely effing with every part isn't necessary.View attachment 826252

This KA7100 though...haven't opened it up but I expect a tear down. I believe you know something about these guys. How's the triac working out?

Same thing with the 7100. WIMAs, KLs, KWs or PWs if you prefer. Make sure you regrease the outputs. I've never used a triac, turn the power switch upside down and use two poles instead of one, and fit a proper spark surpressor.

Lee.