I can understand wanting to keep it original... interesting to see how far you can take it though 
The meters... if it's sticky you could try rigging up a 555 (timer chip as oscillator) to pulse the meter hard and fast to try and free it up.
555 timer IC - Wikipedia, the free encyclopedia
it's the astable bit you want to look at. Run it off a 9 volt battery with a suitable resistor feeding the meter... might help, might not, you just never know. Circuit is that simple it can all be hard wired on to the chip, all for under a couple of squid even at Maplin prices.
The meters... if it's sticky you could try rigging up a 555 (timer chip as oscillator) to pulse the meter hard and fast to try and free it up.
555 timer IC - Wikipedia, the free encyclopedia
it's the astable bit you want to look at. Run it off a 9 volt battery with a suitable resistor feeding the meter... might help, might not, you just never know. Circuit is that simple it can all be hard wired on to the chip, all for under a couple of squid even at Maplin prices.
Thanks for that suggestion Mooly, but I have a feeling it wouldn't help in this instance. I did that multimeter/diode-check deflection test about 50 times in a row, in both directions. The needle always gets stuck in the same spot wehether going from right to left or vice-versa.
I'm thinking I'll have to take those apart (assuming they're not sealed?) and perhaps put a tiny tab of watch-repairers oil or more suitable lubricant on there. There could also be a very tiny bit of grit in the bearings too I guess.
This amp makes me wish I had 8-ohm speakers. The speakers I have are 6-ohm and the meters hardly move at normal listening levels - not a big deal... but they do look cool in action
I'm thinking I'll have to take those apart (assuming they're not sealed?) and perhaps put a tiny tab of watch-repairers oil or more suitable lubricant on there. There could also be a very tiny bit of grit in the bearings too I guess.
This amp makes me wish I had 8-ohm speakers. The speakers I have are 6-ohm and the meters hardly move at normal listening levels
- not a big deal... but they do look cool in action
The meters are sure to come apart, and as previously mentioned the fronts may be held by little more than a strip of sticky tape. That's certainly the case on the TCK5 cassette deck we have.
I know what you mean about the meters moving (or lack of movement) and there's no easy way around that as they are purely "passive". It would need a simple electronic "peak detector and hold" circuit to make them behave more as you would want. Transients in music occur so fast that the caps in the meter circuit can not charge to the full voltage (due to the circuit impedances) and also the meter ballistics are just to slow to respond... so an electronic circuit is the answer. You might get an improvement by using germanium diodes in the meter circuit (0.15 turn on volts as against 0.6ish for silicon).
I know what you mean about the meters moving (or lack of movement) and there's no easy way around that as they are purely "passive". It would need a simple electronic "peak detector and hold" circuit to make them behave more as you would want. Transients in music occur so fast that the caps in the meter circuit can not charge to the full voltage (due to the circuit impedances) and also the meter ballistics are just to slow to respond... so an electronic circuit is the answer. You might get an improvement by using germanium diodes in the meter circuit (0.15 turn on volts as against 0.6ish for silicon).
Talking of meters I built them into my amp too.
I had some "Tandy" (remember them) meters in a stand alone box and always kept them "just in case". Fitted soft red LED backlighting.
Post #283
http://www.diyaudio.com/forums/solid-state/96192-post-your-solid-state-pics-here-15.html#post1417411
http://www.diyaudio.com/forums/solid-state/119151-my-mosfet-amplifier-designed-music.html
I built them into my amp too. I had some "Tandy" (remember them) meters in a stand alone box and always kept them "just in case". Fitted soft red LED backlighting.
Post #283
http://www.diyaudio.com/forums/solid-state/96192-post-your-solid-state-pics-here-15.html#post1417411
http://www.diyaudio.com/forums/solid-state/119151-my-mosfet-amplifier-designed-music.html
Ah you mean this page:
http://www.diyaudio.com/forums/solid-state/96192-post-your-solid-state-pics-here-29.html
VERY nice work indeed Mooly - I bow before your amp building skills! Looks fab, and I imagine from reading that thread it sounds amazing too!
I have several valve 'magic eyes' that I intend to do something with at some point. At some point I want to build another GB150D (miss the one I had to sell last week already!) so I may use these as volume indicators. Remember being mesmerised by them as a kid when I had a Grundig TK20 reel to reel recorder!
Still it's more of an incentive to get this Sony working as if it was brand new. Take what you've got and fly with it, as they say! I think I'll need to replace all those caps sooner rather than later - caught the right channel fading out ever so slightly last night, only dicernable through headphones. I've had this before with an amp that needed a recap and it was fine afterwards. Not surprising with 30+ year old caps in a warm environment (that SMPS puts out quite a bit of heat).
I think a FORTUNE is waiting for some company that invents an electrolytic replacement that never needs replacing. Amazing really that we're still using 'wet' chemical-filled caps in 2011!!!
Was looking at those back-to-back caps last night. Would you mind taking a look at this list Mooly to see that I've got all this correct. I read that two back to back caps results in half the value of one of the caps? I assume all the following caps are directly in the signal path (the only ones which are from what I can see)?
EQ Amp Board: C111/112 - 4.7uF / 50V pair - replace with single 2.2uF film cap
EQ Amp Board: C161/162 - 4.7uF / 50V pair - replace with single 2.2uF film cap
Control Board: C201/214 - 2.2uF / 50V pair - replace with single 1.2uF film cap
Control Board: C251/264 - 2.2uF / 50V pair - replace with single 1.2uF film cap
Control Board: C206/216 - 4.7uF / 50V pair - replace with single 2.2uF film cap
Control Board: C256/266 - 4.7uF / 50V pair - replace with single 2.2uF film cap
- John
http://www.diyaudio.com/forums/solid-state/96192-post-your-solid-state-pics-here-29.html
VERY nice work indeed Mooly - I bow before your amp building skills! Looks fab, and I imagine from reading that thread it sounds amazing too!
I have several valve 'magic eyes' that I intend to do something with at some point. At some point I want to build another GB150D (miss the one I had to sell last week already!) so I may use these as volume indicators. Remember being mesmerised by them as a kid when I had a Grundig TK20 reel to reel recorder!
Still it's more of an incentive to get this Sony working as if it was brand new. Take what you've got and fly with it, as they say! I think I'll need to replace all those caps sooner rather than later - caught the right channel fading out ever so slightly last night, only dicernable through headphones. I've had this before with an amp that needed a recap and it was fine afterwards. Not surprising with 30+ year old caps in a warm environment (that SMPS puts out quite a bit of heat).
I think a FORTUNE is waiting for some company that invents an electrolytic replacement that never needs replacing. Amazing really that we're still using 'wet' chemical-filled caps in 2011!!!
Was looking at those back-to-back caps last night. Would you mind taking a look at this list Mooly to see that I've got all this correct. I read that two back to back caps results in half the value of one of the caps? I assume all the following caps are directly in the signal path (the only ones which are from what I can see)?
EQ Amp Board: C111/112 - 4.7uF / 50V pair - replace with single 2.2uF film cap
EQ Amp Board: C161/162 - 4.7uF / 50V pair - replace with single 2.2uF film cap
Control Board: C201/214 - 2.2uF / 50V pair - replace with single 1.2uF film cap
Control Board: C251/264 - 2.2uF / 50V pair - replace with single 1.2uF film cap
Control Board: C206/216 - 4.7uF / 50V pair - replace with single 2.2uF film cap
Control Board: C256/266 - 4.7uF / 50V pair - replace with single 2.2uF film cap
- John
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Well C205/255 are critical parts in the feedback network around the opamp IC.
C213/263 are in circuit depending if you use the filters etc.
On the phono preamp there is C111/112 and C161/162.
Also C107/157 which actually remove audio but are just as vital as if they passed it.
Caps in series are calculated the same as resistors in parallel.
Caps in parallel the same as resistors in series.
Realistically all the electros should be replaced to be sure although I bet if you test them for increased E.S.R. most will still be excellent. A cap meter is no good as dried out ones would still read the correct value.
C213/263 are in circuit depending if you use the filters etc.
On the phono preamp there is C111/112 and C161/162.
Also C107/157 which actually remove audio but are just as vital as if they passed it.
Caps in series are calculated the same as resistors in parallel.
Caps in parallel the same as resistors in series.
Realistically all the electros should be replaced to be sure although I bet if you test them for increased E.S.R. most will still be excellent. A cap meter is no good as dried out ones would still read the correct value.
Thanks for all that Mooly that's really helpful stuff!
Nearly finished my Word document for all the replacements which are hot-linked to the Farnell website. Makes it so much easier. I should add at this point that I am only replacing ALL electrolytics - everything else (all the film caps already there) will be kept, though I will put in replacement tants where they are already used.
So from that list of back-to-back electrolytics I gave you in post #405, am I correct in saying from your reply above that only C111/112 & C161/162 are in the signal path then? If that's the case it'll save a bit of cash on making them all film caps. So I just need to clarify that is the case...
Thanks again!
- John
P.S. It's sounding REALLY good today!
P.P.S All electrolytics are being replaced with Rubycon ZLGs, give or take the odd one that are only available as Panasonic FC. Would you mind if I sent you my Word document just to make sure I haven't made any silly mistakes, before I pull the trigger on my next Farnell order? No worries if you haven't got the time - I feel I've imposed on you too much already!
Nearly finished my Word document for all the replacements which are hot-linked to the Farnell website. Makes it so much easier. I should add at this point that I am only replacing ALL electrolytics - everything else (all the film caps already there) will be kept, though I will put in replacement tants where they are already used.
So from that list of back-to-back electrolytics I gave you in post #405, am I correct in saying from your reply above that only C111/112 & C161/162 are in the signal path then? If that's the case it'll save a bit of cash on making them all film caps. So I just need to clarify that is the case...
Thanks again!
- John
P.S. It's sounding REALLY good today!
P.P.S All electrolytics are being replaced with Rubycon ZLGs, give or take the odd one that are only available as Panasonic FC. Would you mind if I sent you my Word document just to make sure I haven't made any silly mistakes, before I pull the trigger on my next Farnell order? No worries if you haven't got the time - I feel I've imposed on you too much already!
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I can save it as MS Works, but to be honest I think that covers it all now now I know for sure about those back-to-back caps being in the signal path.
Super-duper
...my wallet is now cowering in fear
I'm kinda curious about how I'm going to do it too hahaha! It's quite low on my list of things to fix, but will have a look at it when I start recapping the EQ and control boards...
Well dare I suggest just sticking with electros as per the original
I been here many times before in the past... it's up to you though
I don't want to influence you either way.
Well being as there are so few electrolytics in the signal path (and then only in the EQ and Control sections) I thought it would be nice to get rid of them altogether, to get the most out of the power-amp section which is DC coupled. From all the reading (and listening) I've done over the years even good electrolytics lag behind film caps, and since I'd only have to buy 6 it seemed worthwhile, not to mention the fact they'd probably last forever without needing to be changed again
Panasonic also do a nice relatively compact polyprolylene cap now which I think will just fit (going to remeasure tomorrow):
PANASONIC|ECWF2225JA|CAPACITOR, 250V, 2.2UF, 5% | Farnell United Kingdom
I would have thought it would be better than any electrolytic?
I can see it will have to be films
They look a bit big...
WIMA|MKS2 2.2UF +/-10% 50V|CAPACITOR, 2.2UF, 50V | CPC
Your Search Results | CPC
They look a bit big...
WIMA|MKS2 2.2UF +/-10% 50V|CAPACITOR, 2.2UF, 50V | CPC
Your Search Results | CPC
I can see it will have to be films
They look a bit big...
WIMA|MKS2 2.2UF +/-10% 50V|CAPACITOR, 2.2UF, 50V | CPC
Your Search Results | CPC
Funnily enough I have several of those on their way to me courtesy of a generous member over at the Pink Fish Media DIY forums. They look quite a bit smaller than those Panasonics. Some people have criticised the sound of the Wimas though so I may end up going for the Panasonics too and have a shoot-out.
Gawd this hobby is exhausting sometimes... wish I'd NEVER heard (!) of the differences between caps. Sometimes ignorance really is bliss. Trying to kick this habit after I've finished the amp.
Place yer bets
Me too! Time for some cider and some music
Thanks a gazillion for all your help again Mooly! I'm listening to the results of all your help right now and it sounds fab
Have a super evening!
- John
P.S. Gadzooks - yeah you're not wrong hahaha!
Whilst listening through headphones this evening, I noticed the sound would sometimes slowly almost disappear from the right channel, then pop back again. This happened the night before too, but only briefly **. The right channel could sometimes distort a little too when the volume decreased for a few seconds.
I suspect 30+ year old caps on their last legs syndrome, as working the switches & turning the controls made no difference.
The amp gets fairly hot in use so I think some of the caps have undoubtedly just about had it.
Have blown £33 on a Farnell order to replace ALL electrolytics (bar the SMPS and PSU board caps which have already been done). Sods law there are a few on back order which won't get here until late March (talk about a SLOW turnaround! Not particularly impressive for a company as huge as Farnell!). I'll just have to put up with that - all good things to those who wait and all that!
Also ordered those trimmer pots, plus the Panasonic polypropylene film caps mentioned a few posts above - looked inside the amp again and worked out they'd JUST fit!
So I think I'd probably better stop using the amp now until the new caps arrive. Don't want anything to go wrong on account of a dicky 30 year old cap just about to go south.
- John
** EDIT: I need to test whether this is just with headphones, or with the speakers as well... Too late to test the speakers tonight. One for the morning...
I suspect 30+ year old caps on their last legs syndrome, as working the switches & turning the controls made no difference.
The amp gets fairly hot in use so I think some of the caps have undoubtedly just about had it.
Have blown £33 on a Farnell order to replace ALL electrolytics (bar the SMPS and PSU board caps which have already been done). Sods law there are a few on back order which won't get here until late March (talk about a SLOW turnaround! Not particularly impressive for a company as huge as Farnell!). I'll just have to put up with that - all good things to those who wait and all that!
Also ordered those trimmer pots, plus the Panasonic polypropylene film caps mentioned a few posts above - looked inside the amp again and worked out they'd JUST fit!
So I think I'd probably better stop using the amp now until the new caps arrive. Don't want anything to go wrong on account of a dicky 30 year old cap just about to go south.
- John
** EDIT: I need to test whether this is just with headphones, or with the speakers as well... Too late to test the speakers tonight. One for the morning...