I m back on the hunt for that naughty resistor.
Thanks
If your family is near by, and needs any help with their computers I'll help them out. I really appreciate what you are doing for me.
Ben
Thanks
If your family is near by, and needs any help with their computers I'll help them out. I really appreciate what you are doing for me.
Ben
Be careful if you have dc. Trouble shoot without speakers connected . DC can fry your coils quite fast.
Doesn't the circuit have a dc protection circuit ?
After you sort out the dc problem , you could connect the speakers.
Doesn't the circuit have a dc protection circuit ?
After you sort out the dc problem , you could connect the speakers.
high bias
for the bias problem, you might want to check the heat sink grease on the bias transistor. once the grease dries out it's difficult for the bias transistor to accurately sense the heat sink temperature. if the heat sink grease under the bias transistor is crumbly, clean it off and replace it with fresh grease, and you might as well go ahead and replace the grease on the output transistors too. i do refurbs of vintage amps, and this is one of the things i do that most techs overlook.
for the bias problem, you might want to check the heat sink grease on the bias transistor. once the grease dries out it's difficult for the bias transistor to accurately sense the heat sink temperature. if the heat sink grease under the bias transistor is crumbly, clean it off and replace it with fresh grease, and you might as well go ahead and replace the grease on the output transistors too. i do refurbs of vintage amps, and this is one of the things i do that most techs overlook.
located and located and open and open
Dam your good
2 10ohm 1/4 watters NG
Thanks unc grease is thermal paste is good!
for entertainment
http://www.gargaro.com/marvinsounds.html
Dam your good
2 10ohm 1/4 watters NG
Thanks unc grease is thermal paste is good!
for entertainment
http://www.gargaro.com/marvinsounds.html
Hi Ben,
I've seen lot's of those open. That indicates current flow between grounds and I can't figure out how someone does that.
Your bias transistors will be fine unless you lift them, then you must replace the grease.
If you are going to regrease your output stages, set aside a lot of time and a clean work area. You will need new mica insulators and some new, reasonably fresh thermal compound. Wakefield 120 is preferred. There are some insulator bushings on the end transistors, watch you don't lose them. Clean all mounting hardware in some lacquer thinner. Take pictures as you go!
While you are at it, measure the beta of the outputs and try to group them by beta. Check leakage if you can. Make sure you clean all the old grease off. Lacquer thinner works very well. It also is good to clean any flux off.
You will also give your iron, solder sucker and wick a work out. Understand this job is good for 4~5 hours to do it right. If you are unwilling to spend this time and don't have a reason to go in there, don't do it.
So Ben, understand that this is a grueling job. You won't like it. 😉 I find it boring to do, and I've done more than a few.
-Chris
I've seen lot's of those open. That indicates current flow between grounds and I can't figure out how someone does that.
Your bias transistors will be fine unless you lift them, then you must replace the grease.
If you are going to regrease your output stages, set aside a lot of time and a clean work area. You will need new mica insulators and some new, reasonably fresh thermal compound. Wakefield 120 is preferred. There are some insulator bushings on the end transistors, watch you don't lose them. Clean all mounting hardware in some lacquer thinner. Take pictures as you go!
While you are at it, measure the beta of the outputs and try to group them by beta. Check leakage if you can. Make sure you clean all the old grease off. Lacquer thinner works very well. It also is good to clean any flux off.
You will also give your iron, solder sucker and wick a work out. Understand this job is good for 4~5 hours to do it right. If you are unwilling to spend this time and don't have a reason to go in there, don't do it.
So Ben, understand that this is a grueling job. You won't like it. 😉 I find it boring to do, and I've done more than a few.
-Chris
I'm just going to replace the resistors. If it ain't broke don't fix it. Except old caps. I'll be back at it later today.
Thanks Ben
Thanks Ben
Hi Ben,
You mean the resistors? Right? 😉
Do check the bias current, reduce if it's running too warm.
-Chris
You mean the resistors? Right? 😉
Do check the bias current, reduce if it's running too warm.
-Chris
yes I had to do a quick edit. I am very tired today. Not much sleep. I have a pair of Polk SDA2's on the way here via Fed Ex. Is it wrong to pray for speakers? I have had them ruin things on me before.
Ben
Did you get the Martian link?
Ben
Did you get the Martian link?
Hi Ben,
I must say that speakers often don't travel well. I wish you luck!
Funniest (sad I guess) speaker shipment. A pair of Carver Amazing's shipped in Canada during the winter. All those magnets broke free.
Man, what a mess! Two new panels coming up! I've seen them broken into two pieces as well. Panels toast yet again.
-Chris
Actually, I forgot about it! LMAO! It's a riot, thanks!
I must say that speakers often don't travel well. I wish you luck!
Funniest (sad I guess) speaker shipment. A pair of Carver Amazing's shipped in Canada during the winter. All those magnets broke free.
Man, what a mess! Two new panels coming up! I've seen them broken into two pieces as well. Panels toast yet again.-Chris
I got my SDA2's, and a book the SDA line of speakers. Both in good shape. Listening to some carlos santana for the moment.🙂
Hi Ben,
I know I mentioned this at the Polk forum and read that you are using a GFA-555 to run your SDA's at the moment. Just remember that most SDA's of that generation need to be powered by common ground amps. I'm pretty sure the 555 is but I'm pretty sure the 585 is NOT.
Hi Chris, great advice as always I knew when I refered him here you guys would help him out. 😎
Brock
I know I mentioned this at the Polk forum and read that you are using a GFA-555 to run your SDA's at the moment. Just remember that most SDA's of that generation need to be powered by common ground amps. I'm pretty sure the 555 is but I'm pretty sure the 585 is NOT.
Hi Chris, great advice as always I knew when I refered him here you guys would help him out. 😎
Brock
Hi Brock,
The GFA-585 is common ground, so no worries there. If memory serves, the only Adcom that wasn't common ground was the GFA-1 and 1A, they were bridged. Even the GFA-565 (mono) is common ground.
Thanks Brock! 😉 (I used to do Polk warranty service as well, Polks and some Carver amps should be avoided for that ground issue).
-Chris
The GFA-585 is common ground, so no worries there. If memory serves, the only Adcom that wasn't common ground was the GFA-1 and 1A, they were bridged. Even the GFA-565 (mono) is common ground.
Thanks Brock! 😉 (I used to do Polk warranty service as well, Polks and some Carver amps should be avoided for that ground issue).
-Chris
Thanks for the clarification. I do believe you and I have discussed this subject before and it is my understanding the the newer Mosfet Adcom's 5xxx are not common ground.
I believe the 5500, 5800, 5802 are not common ground because they have secondary windings. For my own info does this sound correct to you? This comes up quite a bit on the Polk forum and although my advise is to always consult the manufacturer maybe you could shed some light on the subject.
Thanks
Brock
I believe the 5500, 5800, 5802 are not common ground because they have secondary windings. For my own info does this sound correct to you? This comes up quite a bit on the Polk forum and although my advise is to always consult the manufacturer maybe you could shed some light on the subject.
Thanks
Brock
Hi Brock,
I don't believe you should have any problems with those. You need to link the negative speaker terminals together or you will wipe out the input grounds.
I would suggest a technician (a good one!) permanently links the negative terminals together. This is from memory on this problem, and I do remember it clearly. There should be no other issues but the ground linking issue.
How's that for an answer?
-Chris
I don't believe you should have any problems with those. You need to link the negative speaker terminals together or you will wipe out the input grounds.
I would suggest a technician (a good one!) permanently links the negative terminals together. This is from memory on this problem, and I do remember it clearly. There should be no other issues but the ground linking issue.
How's that for an answer?
-Chris
Hi Brock,
Otherwise, the Adcom amps are very good ones to drive those speakers. The need for a common ground was unanticipated by many manufacturers. The SDA was an odd speaker setup and caused many problems for more than one product line. The fact that many salespeople selling the Polks were poorly educated was only matched by the number of people who did not read the product information in the box.
-Chris
Otherwise, the Adcom amps are very good ones to drive those speakers. The need for a common ground was unanticipated by many manufacturers. The SDA was an odd speaker setup and caused many problems for more than one product line. The fact that many salespeople selling the Polks were poorly educated was only matched by the number of people who did not read the product information in the box.
-Chris
Now I am confused. Should the grounds on the inputs be tied together. I see that the speakers are sharing their grounds, and that the 10ohm resistors kinda tie the input grounds together. Should I tie the input grounds together at the jacks?
I am running SDA2's, and plan to run SDA-SRS or SDA1.2TL's in the future.
Thanks Ben
I am running SDA2's, and plan to run SDA-SRS or SDA1.2TL's in the future.
Thanks Ben
Hi Ben,
NO!!!!!!!!! 😉
Measure the resistance between the black speaker terminals. It should be a short (0 ohms or whatever your leads read when they are touching together).
-Chris
NO!!!!!!!!! 😉
Measure the resistance between the black speaker terminals. It should be a short (0 ohms or whatever your leads read when they are touching together).
-Chris
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