Having an Issue with this Amp, it powers on *in theory*, I hear the relay for the ease-in click, and nothing else happens.
BUT if I take a hair dryer, and heat up the heat-sink and the board after about 50 seconds on high heat, it powers on with no issues and gives continuous use without fail. once it's turned off again, same problem.
does anyone have Ideas on what would cause this?
BUT if I take a hair dryer, and heat up the heat-sink and the board after about 50 seconds on high heat, it powers on with no issues and gives continuous use without fail. once it's turned off again, same problem.
does anyone have Ideas on what would cause this?
cal: sorry, I've been going to so many forums and reading over every bit of info I can, I have this piece and I'm attempting something else which I may also post about later, I got a little impatient since after everywhere I went I realized I might actually get some half decent answers here lol.
after looking over the schematic for the 5th time, I can't find anything attached to the heatsink, but I did happen to notice a protection switch indicated, which I cannot locate in the schematic. I'm going to keep looking, but if anyone can think of another reason for something like this to happen, I'd appreciate the input. this amp was a x-mas gift, if I can't get it to fire up on switch, I may just Gut it for parts...
after looking over the schematic for the 5th time, I can't find anything attached to the heatsink, but I did happen to notice a protection switch indicated, which I cannot locate in the schematic. I'm going to keep looking, but if anyone can think of another reason for something like this to happen, I'd appreciate the input. this amp was a x-mas gift, if I can't get it to fire up on switch, I may just Gut it for parts...
looked it over more intensely, there are 2 varistors screwed to the bottom of the heat-sink, but they're for voltage overload situations, still nothing dealing with overheating.
as a side note before I got the amp apparently it would power on fine and drop while it was on, is it possible the problem I'm having now stemmed from that issue? I would imagine so, but it seems like 2 extreme opposite issues.
as a side note before I got the amp apparently it would power on fine and drop while it was on, is it possible the problem I'm having now stemmed from that issue? I would imagine so, but it seems like 2 extreme opposite issues.
ok after messing around with some frozen beef and my g/f's hairdryer, I've pretty much determined that it's the varistors, any canucks know a good online source for electronic parts in canada? I've been looking around and I can't find any place that I can order parts, or replacement parts from.
I did that today to no avail, I didn't find any cold solders, but I Re-soldered a bunch anyway just to be sure, I either have to bypass the varistors or order new ones... which sucks because they're 5 bucks a piece USD from the only site I could find them, and they don't ship to canada >.<
these guys are a DIY'ers best bet I ordered a small box of stuff late one afternoon here in B.C. and the UPS man was ringin' my bell... THE NEXT DAY!!!
8 bucks shipping and no surprises by UPS holding their hand out for money. It was my most satisfting internuts purchase ...EVER!
...spend $200 and shipping is FREE!
went to the site, just spent 2 hours trying to locate anything remotely similar to what I'm looking for, which would be a modern replacement for a STV3H-Y Varistor which mounts onto the bottom of the heat-sink. If you can find my one with the same values as the partnumber stated, please hyperlink it, because I obviously have no clue what I'm looking for, if what their site has for parts is right...
Pioneer SA-6800 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine theres the schematic, the info is down toward the bottom for anyone who might want to help further, you have to log in to get the schem but it's free.
from what you have said the amp doesnt power on when its cold correct?
Ive not looked through any of pioneers newer designs (newer than 1975) but i do recall on nelsons pass' DIY page "the amazing FET circolotron" uses tempeture coefficient resistors (the resistance value changes with tempeture) this would to me at least be something to look for if it has to get hot to turn on (resistance being too high until it is warmed for the circuits to receive their proper operating voltage)
Ive not looked through any of pioneers newer designs (newer than 1975) but i do recall on nelsons pass' DIY page "the amazing FET circolotron" uses tempeture coefficient resistors (the resistance value changes with tempeture) this would to me at least be something to look for if it has to get hot to turn on (resistance being too high until it is warmed for the circuits to receive their proper operating voltage)
Just a note, it's the Power amps, should I bother replacing them or just toss the unit? I'm pretty much at peak frustration now, I just want something that works...
2SB705A/2SD745A pair.
and if anyone would like to recommend a modern replacement, I'm open to suggestions. otherwise I'll rip it apart and burn everything... or if my frustration levels go down maybe buy some decent Parts and build a modern amp instead.
thanks for the help to this point anyway.
2SB705A/2SD745A pair.
and if anyone would like to recommend a modern replacement, I'm open to suggestions. otherwise I'll rip it apart and burn everything... or if my frustration levels go down maybe buy some decent Parts and build a modern amp instead.
thanks for the help to this point anyway.
Reading through the manual,(taking note its a dc detector) and provided your systems.
Im guessing you have a voltmetre laying around somewhere.
Disconnect your speakers and secure the probes to the terminals (you might want to use a resistor anything 8 to 32 ohm). set the volt metre to dc (peak hold) and warm it up then turn it on.
If it gives you a moderate reading(i suspect it will) then this indicates of course that there is dc flowing to the output which trips the protection.
If this is the case in a regular DIY amp i would say start out by replacing all your caps : /
but since its not it could be coming from anywhere. a burned up diode thats bridged its contacts. a foremention cap thats brokedown or worn out ect ect.
but IMO (and yes i know how frustrating this canbe) your giving up too easily.
but theres a good starting point for the diagnoses.
Im guessing you have a voltmetre laying around somewhere.
Disconnect your speakers and secure the probes to the terminals (you might want to use a resistor anything 8 to 32 ohm). set the volt metre to dc (peak hold) and warm it up then turn it on.
If it gives you a moderate reading(i suspect it will) then this indicates of course that there is dc flowing to the output which trips the protection.
If this is the case in a regular DIY amp i would say start out by replacing all your caps : /
but since its not it could be coming from anywhere. a burned up diode thats bridged its contacts. a foremention cap thats brokedown or worn out ect ect.
but IMO (and yes i know how frustrating this canbe) your giving up too easily.
but theres a good starting point for the diagnoses.
Thanks for the encouragement, I took auto motive electrical in college, and I've been messing around with diy projects and home fixes for a while now, I just can't seem to grasp some concepts that are vital to diagnosis. And to be honest, for me that's extra frustrating, because I can sit in a car and within a 10 minute ride tell you everything that needs to be fixed for safety (beside body work obviously) without even looking under the hood. >.< oh well, I'm going to snag a new voltmeter up with my tax money, the last one I had went missing 2 years ago :-/ I'll update when I know more... thanks again, at least I don't have to assume it's an un-obtainable part now.
do some reading machines like that at this age sufer from a gozillion problems .... and take my word for it THERE IS NO VARISTORS INSIDE ....
beyond solder joints that you are not able to see all capacitors inside are simply history there is no question about that ...its just a simple fact
so to put this amchine to life you need parts , procedure , a bit of knowledge , be able to follow procedure and read this
( to my understanding you dont stand a chance but at least you get my help and others from the forum )
my best advice will be to give it to an expert
all the help you need is here http://www.diyaudio.com/forums/solid-state/136261-vintage-amplifier-repair-upgrade-manual.html
if you are able to read understand and execute that after a couple of days of work and no more than 20 usd you are going to have your shelf a perfectly working and sounding amp ....
trust me it is writen in plain .....greek ....
beyond solder joints that you are not able to see all capacitors inside are simply history there is no question about that ...its just a simple fact
so to put this amchine to life you need parts , procedure , a bit of knowledge , be able to follow procedure and read this
( to my understanding you dont stand a chance but at least you get my help and others from the forum )
my best advice will be to give it to an expert
all the help you need is here http://www.diyaudio.com/forums/solid-state/136261-vintage-amplifier-repair-upgrade-manual.html
if you are able to read understand and execute that after a couple of days of work and no more than 20 usd you are going to have your shelf a perfectly working and sounding amp ....
trust me it is writen in plain .....greek ....
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