AX-700

I just got through with the recap of a Pioneer SX-8 and had the same findings with regards to the caps.
Out of about 40 caps I replaced, 6 were lower than spec (but still within 20%) and only a single one was significantly down (2200uF was 1300uf tested). In my case I had to replace a few regulators as well but wasn't about to leave old caps in there once I got through the labyrinth of boards and wires to access the regs.
It really goes to show why all of the caps should be replaced if you want reliable long term operation out of older gear. Sure most are probably good but an increasing number are not and you have no idea where the out of spec ones are hiding and what mischief they are causing.
We spend a lot of time and effort (not to mention $) on these units but it's well worth it IMO.
 
I just got through with the recap of a Pioneer SX-8 and had the same findings with regards to the caps.
Out of about 40 caps I replaced, 6 were lower than spec (but still within 20%) and only a single one was significantly down (2200uF was 1300uf tested). In my case I had to replace a few regulators as well but wasn't about to leave old caps in there once I got through the labyrinth of boards and wires to access the regs.
It really goes to show why all of the caps should be replaced if you want reliable long term operation out of older gear. Sure most are probably good but an increasing number are not and you have no idea where the out of spec ones are hiding and what mischief they are causing.
We spend a lot of time and effort (not to mention $) on these units but it's well worth it IMO.

Agree. Well worth the effort. At the moment I'm a bit mystified as to why all of a sudden many values of Nichicon caps are suddenly drying up. And Mouser is showing lead times of 20-22 weeks for backorder. And clearly people are scrambling to find anything that fits. I'm watching one cap after the other dissapear right up the voltage chain as people do what I did and buy the next step (or 2 or 3) up. I have 3 amps sitting here that could be finished in a few hours that are waiting for caps. WTF?

Cheers,
James
 
That is odd. I just made a 5 page order of Nichicon caps from Digikey last week and had no backordered parts at all. Maybe Mouser is having a supply issue with Nichicon right now?
 
As a newbee, one of the things, among so many things, I am trying to get my head around is which caps to use.

As the saying goes, it's all relative.

Clearly the filter caps need to be low ESR Caps.

For everything else, can we use the FG series without stressing them or the board with heat?

Is the ESR rating on the FG caps equal or lower than the factory original ESR rating on the factory supplied caps?

I think someone said the for less than 10uf we should just replace with Polyprop. caps. Does this cover all coupling caps?

On the A-1000 I have been studying, on the audio path highlighted on the schematic, if I read it correctly there are only 4 caps in the (2) audio paths, the rest are in the power circuits and coupling the transistors.

I am building up a bill of materials BOM for the A-1000 and will likely include some parts even if I don't need them on this project so as to identify the replacements for other projects going forwards.



Thanks!
 
That is odd. I just made a 5 page order of Nichicon caps from Digikey last week and had no backordered parts at all. Maybe Mouser is having a supply issue with Nichicon right now?

Thanks for the heads up. I haven't been ordering from DigiKkey as their prices were a good bit higher than Mouser but I'll check there now. Waiting a long time sucks more than paying more.

Cheers,
James
 
It's ok, James. For the input cap it can be quite flexible. Actually this is an opportunity to make some experiments and research: you can use another value from 1uF up to 10uF (for both channels) and see how it sounds, comparing this silver 700 with the black 700.

In some amps I modified the stock input capacitance because I found the overall sound a bit crispy, harsh, etc. Any cap in that range (1uF-10uF) can be use for experiment purposes.

Oh man, sorry about that! I thought it was the 4.7uF ones...

On the other hand, I don't have any 33µF 16v caps and will have to order them. But I do have some 47µF 16v on hand. Do you think that that would be a dangerous leap to try substituting them? After all, that's what is called for in the SM, although the positions of the small & large caps are reversed.

Cheers,
James
 
One of the things I am trying to do is get some measurements on the systems.

I need to get a dummy load now that I have a signal generator so that I can measure the volts out at full amplitude, there is a PC based product I am experiment with called Virtual Analyzer that uses the RCA jacks as the input to the AD converter.

If I understand it correctly RCA is limited to 3 volts, there is also the issue of limiting current to be considered.

Does anyone know the measurement of say a 100 watt amps output in volts and current? I am trying to figure out how to interface to my PC and VA.

Thanks
 
Hi Mark, you are way ahead of me, I've yet to even make a dummy load (although I have at least found a nice large piece of heat sink to start with). But I will be interested in hearing what you find out.

Cheers,
James
 
Hi Mark, you are way ahead of me, I've yet to even make a dummy load (although I have at least found a nice large piece of heat sink to start with). But I will be interested in hearing what you find out.

Cheers,
James

Update below, my math was wrong.....

or six 24 ohm 100W non inductive resistors, two sets of 3, wired in parallel so that you can test a 300W amp or less. I think I have seen them for $10 ea or less if you look around. The ones with the extruded heat sink skins not only look cool but probably have good cooling............

Once they are configured, I can start playing with my oscilloscope and the speaker outputs under load. Will also look at stacking banana plugs in an effort to also connect to the PC RCA interfaces at the same time to calc THD and look at the spectrum, will likely require an intermediate circuit to protect the PC

http://www.amazon.com/Amico-Mounted-Aluminum-Wirewound-Resistors/dp/B008MKZMIU/ref=pd_cp_hi_1?ie=UTF8&refRID=1PGX138GTM5V24JXESKR
 
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This is the PC freeware, which is very cool.

You can use it right away by connecting to the line out RCA to the mic, and the Signal generator to the Aux port on the Inputs of the amp. I run my pc speakers at the same time so I can hear the signal. I would have to look, but the line out probably bypasses the tone controls in the pre amp section.

This is a no brainer, download it and start playing with it, very cool.

index.7.jpg



VA web site
http://www.sillanumsoft.org/


Download site with comments
http://www.hitsquad.com/smm/programs/VA/

DIY site with comments
http://www.diyaudio.com/forums/software-tools/212908-exploring-visual-analyser-va.html

Sound Card Interface discussion
http://www.diyaudio.com/forums/equipment-tools/213451-audio-test-bench-control-unit.html

http://www.diyaudio.com/forums/tubes-valves/155405-test-measurement-interface-soundcard.html

DIY interface unit kit
http://www.pmillett.com/ATEST.htm

Various info in Italian inc articles
http://casa.accattatis.org:9090/Articoli%20su%20VA%20--%20Articles%20on%20VA/?date

User written Documentation and how to use, very nice.
http://www.mcgee-flutes.com/VA-Intro.htm

http://www.mcgee-flutes.com/Visual-Analyser-Oscilloscope.htm
 
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For home, you should be able to buy a quality used analog techtronics oscilloscope for $100.

My EE friend gave me one on permanent loan to play with, two channels and plenty of bandwidth for the freqs in audio gear. He purchased it at work for $25 when they were getting rid of them ten years ago. Works perfectly and is basic which is what I need.

Anyway, the techtronics probes are probably fabulous, also very expensive, for what we are doing these are good enough, I just ordered a pair.

http://www.amazon.com/gp/product/B0030KWM30/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
 
Bubo,
If you put three 8ohm resistors in parallel, the your amp is only going to see a 2.67 ohm load:no:, not the 8 ohms you want. You could get three 24ohm (100 watt) resistors in parallel, then your amp would see an 8 ohm load. :thmbsp:
Resistance in parallel: Rtotal = 1/(1/R1 + 1/R2 + 1/R3)
 
Bubo,
If you put three 8ohm resistors in parallel, the your amp is only going to see a 2.67 ohm load:no:, not the 8 ohms you want. You could get three 24ohm (100 watt) resistors in parallel, then your amp would see an 8 ohm load. :thmbsp:
Resistance in parallel: Rtotal = 1/(1/R1 + 1/R2 + 1/R3)

Thanks, the Reciprocal Formula

8 Ohm x 3 parallel circuit

1/ (1/8 + 1/8 + 1/8)

1/ (.125 + .125 + .125) = 1/.375 = 2.66666etc

24 ohm x3

1/ (1/24 + 1/24+ 1/24) = 1/ ( .0416 + .0416 + .0416 ) = 1/ .125 = 8 Ohm

Thanks for the heads up.
 
That 8ohm - 300watt resistor will work. It'll make a nice 300 watt heater for you workshop, as long as long as you amp is good for it :D You could get two of those resistors and be able to test both channels at once, with the added benefit of being able to test one channel at 4 Ohms if you wire them in parallel.:thmbsp:
 
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