Okay, I was inspired by Vikash's webpage: http://www.vikash.info/audio/gainclone/
So, I headed to ebay and a garage sale today... here is what we got so far:
For $7 at a garage sale, I picked up this receiver (Kenwood KR-3130) -- picture attached. I will post a few more pics in reply so you can see the back and insides for inspiration
And this (again Kenwood) KA 2002a http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=9735051395&rd=1&sspagename=STRK:MEWN:IT&rd=1
Lemme just start with question #1, I figure there will be 86 by the time I am done
With reguard to the transformer: am I better off taking some measurements before tearing it out of the receiver? On the 3130, I see no markings on the transformer... someone I need to figure out what is up with it
So, I headed to ebay and a garage sale today... here is what we got so far:
For $7 at a garage sale, I picked up this receiver (Kenwood KR-3130) -- picture attached. I will post a few more pics in reply so you can see the back and insides for inspiration
And this (again Kenwood) KA 2002a http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=9735051395&rd=1&sspagename=STRK:MEWN:IT&rd=1
Lemme just start with question #1, I figure there will be 86 by the time I am done
With reguard to the transformer: am I better off taking some measurements before tearing it out of the receiver? On the 3130, I see no markings on the transformer... someone I need to figure out what is up with it
Attachments
Ya, should have clarified the goal
Just like Vikash, on his project at http://www.vikash.info/audio/gainclone/ I want to jump in and learn something by building a simple gainclone... using the cheapest parts humanly possible (with the idea of building a non-ghetto one the 2nd go around).
So, trying to figure out what parts I can salvage out of these two receivers.
Just like Vikash, on his project at http://www.vikash.info/audio/gainclone/ I want to jump in and learn something by building a simple gainclone... using the cheapest parts humanly possible (with the idea of building a non-ghetto one the 2nd go around).
So, trying to figure out what parts I can salvage out of these two receivers.
Ok, the transformers would be good if they give the right voltages. If not sure of the units you will be pulling them from, it might be safest to pull them then measure them.
Keep in mind that the DC rails obtainable from them will in theory be 1.4 times higher than the measured AC RMS voltages. In practice they will be a little less than this due in part to the limited size of the smoothing caps, and in part to the trasnsformer being loaded. Think in the order of 10% give or take 10% (estimate only).
Oh, and what about heatsinks, volume pot, switches, case. Have you thought about transplanting them into one of these cases? The existing ground platform, mains switching and fusing arrangement might take a little of the pressure off.
Keep in mind that the DC rails obtainable from them will in theory be 1.4 times higher than the measured AC RMS voltages. In practice they will be a little less than this due in part to the limited size of the smoothing caps, and in part to the trasnsformer being loaded. Think in the order of 10% give or take 10% (estimate only).
Oh, and what about heatsinks, volume pot, switches, case. Have you thought about transplanting them into one of these cases? The existing ground platform, mains switching and fusing arrangement might take a little of the pressure off.
Okay, lets do some learning people! (well, you guys do the teaching, I will do the learning )
Attached a new pic, from the underside of the amp. I busted out my voltmeters and started measuring random stuff, most of which I didn't understand
Mr Transformer has 4 pretty colors coming in (white, red, blue and yellow) and 4 pretty colors coming out (2xred, blue and black).
The two reds... head on over to that goofy 4-legged black device in the middle. Legs are marked + ~ ~ - Now, I am not genius, but it seems this device converts AC to DC!
rectifier I assume?
Measure across the two reds, I am getting about 38v AC. So, I assume this says something important about my transformer
Now, here is where I get pretty confused.
Measure across the DC legs... I get about 47v DC. I sorta expected more like 53 (38v * 1.4 ~= 53v). Then on a whim, I measured the DC legs... while switching trusty multi-meter over to AC mode. It measures 105v AC. was i expecting that?
You can see a black'ish circle to the left of Mr 4 Legs, that is the 50v, 1000uF cap (and is where the dc legs head off to, in parallel to their other travels... makes sense... smooth cap, right?).
The blue/black wires from the transformer headed off to an output selector (A, B, or A+B), and I believe come back to those two 35v 1000uF caps. Haven't looked really hard at that part yet.
---
edit: Crap, it won't let me attach. Doesn't give an error, just doesn't show up. Will try again later I guess.
)Attached a new pic, from the underside of the amp. I busted out my voltmeters and started measuring random stuff, most of which I didn't understand
Mr Transformer has 4 pretty colors coming in (white, red, blue and yellow) and 4 pretty colors coming out (2xred, blue and black).
The two reds... head on over to that goofy 4-legged black device in the middle. Legs are marked + ~ ~ - Now, I am not genius, but it seems this device converts AC to DC!
rectifier I assume?
Measure across the two reds, I am getting about 38v AC. So, I assume this says something important about my transformer
Now, here is where I get pretty confused.
Measure across the DC legs... I get about 47v DC. I sorta expected more like 53 (38v * 1.4 ~= 53v). Then on a whim, I measured the DC legs... while switching trusty multi-meter over to AC mode. It measures 105v AC. was i expecting that?
You can see a black'ish circle to the left of Mr 4 Legs, that is the 50v, 1000uF cap (and is where the dc legs head off to, in parallel to their other travels... makes sense... smooth cap, right?).
The blue/black wires from the transformer headed off to an output selector (A, B, or A+B), and I believe come back to those two 35v 1000uF caps. Haven't looked really hard at that part yet.
---
edit: Crap, it won't let me attach. Doesn't give an error, just doesn't show up. Will try again later I guess.
Sillyboy said:
Is there also a ground somewhere in there -- ie is the 38 V really +19VAC, -19VAC (ideal for a GC) or is it 0-38VAC (not so good)
Does the amp actually work? on the DC side you should only be measuring the ripple, which with a working smoothing cap should be considerabley less than 105V
That can't be right. What do you measure across the blue/black? Is there a voltage across red/black, or red/blue?
That points towards (+19)-0-(-19) AC rails
dave
Part of the problem is that I have (apparently) no idea what I am doing.
If I set my multi-meter to AC... and take a measurement... I would think that swapping the probes would have no effect. Alas, that is sometimes not the case for me!
Example, measuring across red/blue from transformer output:
- using DC, I get 18v.
- using AC... I get well, 4 values...
blue vs red1: 40v
blue vs red2: 47v
red1 vs blue: 0v
red2 vs blue: 6v.
Anybody want to explain this?
In other voltages:
- blue/black: 7v ac (consistent across swaps, and measure 0v DC)
- red/black: again, crazy: 18vdc -- and measures 41vac 1 way, 0vac the other (consistent between both reds).
As far as ground goes... I'm not qualified to say I am fairly sure the black wire coming out of the transformer is black, as I can simply use the chassis, instead of the black wire... in all cases. What does this imply?
Oh, and I had never tried it out... so I actually hooked up a speaker only station I could get.... Rush Limbaugh! Eeck! but the amp worked fine.
And... slightly tangental, but since you commened on it... voltage across the 35v caps... both show 23vdc across them. I, of course, have no idea why there are 2. A vs B speaker sets... or 2 rails... or something else
Seems to me that my multi-meter just gets grumpy if I measure AC, when there is a dc current? I double checked across the smoothing cap: 47vdc, 105vac one way, but swap, and get 0vac.
Hopefully attachments start working again soon. Will attach here again, just in case
If I set my multi-meter to AC... and take a measurement... I would think that swapping the probes would have no effect. Alas, that is sometimes not the case for me!
Example, measuring across red/blue from transformer output:
- using DC, I get 18v.
- using AC... I get well, 4 values...
blue vs red1: 40v
blue vs red2: 47v
red1 vs blue: 0v
red2 vs blue: 6v.
Anybody want to explain this?
In other voltages:
- blue/black: 7v ac (consistent across swaps, and measure 0v DC)
- red/black: again, crazy: 18vdc -- and measures 41vac 1 way, 0vac the other (consistent between both reds).
As far as ground goes... I'm not qualified to say
I am fairly sure the black wire coming out of the transformer is black, as I can simply use the chassis, instead of the black wire... in all cases. What does this imply?Oh, and I had never tried it out... so I actually hooked up a speaker
only station I could get.... Rush Limbaugh! Eeck! but the amp worked fine.And... slightly tangental, but since you commened on it... voltage across the 35v caps... both show 23vdc across them. I, of course, have no idea why there are 2. A vs B speaker sets... or 2 rails... or something else
Seems to me that my multi-meter just gets grumpy if I measure AC, when there is a dc current? I double checked across the smoothing cap: 47vdc, 105vac one way, but swap, and get 0vac.
Hopefully attachments start working again soon. Will attach here again, just in case
Word is... attachments are fixed.
I have re-read planet's comment like 3 times, and it is just now sinking in.
+..........X....??
- ..........X....??
Say X are the points I am measuring, maybe at the legs of mr 4 leg (that really is a rectifier, right?)...
The point is that w/o knowing what what else X is connected to... I can't really accurately measure. The ?? represents the scary unknown
Okay, so... uh... do I really have to disconnect things to measure them?!
I have re-read planet's comment like 3 times, and it is just now sinking in.
+..........X....??
- ..........X....??
Say X are the points I am measuring, maybe at the legs of mr 4 leg (that really is a rectifier, right?
)...The point is that w/o knowing what what else X is connected to... I can't really accurately measure. The ?? represents the scary unknown
Okay, so... uh... do I really have to disconnect things to measure them?!
Attachments
Yep, you read that correctly, C1060.
<sigh> I have been googling like mad -- but everywhere "output transistor" is used... it seems to be with the assumption that you already know what it is. Somebody want to enlighten me (or send me a link, or recommend a book since I finally got a library card yesterday)
And let's not forget: the most important question we have currently running is about my transformer: how do I know if its +19vac,-19vac vs (nastier) 0-38vac?
<sigh> I have been googling like mad -- but everywhere "output transistor" is used... it seems to be with the assumption that you already know what it is. Somebody want to enlighten me (or send me a link, or recommend a book since I finally got a library card yesterday
)And let's not forget: the most important question we have currently running is about my transformer: how do I know if its +19vac,-19vac vs (nastier) 0-38vac?
Can you measure between each red lead and the chassis with your meter in AC mode?
Output transistors are the devices which supply power to the load (in this case, your speakers).
With regard to books, I use "The Art of Electronics" by Horowitz & Hill as a constant reference.
ISBN 0 521 23151 5 (Hardcover)
ISBN 0 521 29837 7 (Paperback)
It covers everything from basic DC theory to digital computers.
Cheers
Rob
Output transistors are the devices which supply power to the load (in this case, your speakers).
With regard to books, I use "The Art of Electronics" by Horowitz & Hill as a constant reference.
ISBN 0 521 23151 5 (Hardcover)
ISBN 0 521 29837 7 (Paperback)
It covers everything from basic DC theory to digital computers.
Cheers
Rob
Shouldn't that read asillyscope
Seriously though, those readings make no sense at all.
Let's try a different approach.
With the power off and unplugged, measure the resistance between each red lead and chassis using the lowest ohms range on your meter. Then reverse the leads and measure it again.
Cheers
Rob
Seriously though, those readings make no sense at all.
Let's try a different approach.
With the power off and unplugged, measure the resistance between each red lead and chassis using the lowest ohms range on your meter. Then reverse the leads and measure it again.
Cheers
Rob
Been looking back over all the evidence.
It looks like one side of this capacitor is connected to chassis - right?
Coupled with the fact that all of the output transistors are the same, it suggests to me that you have a quasi-complementary (Google it) output stage with a single supply.
The clincher will be if you can trace the +/red speaker terminal back to a capacitor.
If that's the case, it's not looking good for a potential chip-amp power supply.
Cheers
Rob
It looks like one side of this capacitor is connected to chassis - right?
Coupled with the fact that all of the output transistors are the same, it suggests to me that you have a quasi-complementary (Google it) output stage with a single supply.
The clincher will be if you can trace the +/red speaker terminal back to a capacitor.
If that's the case, it's not looking good for a potential chip-amp power supply.
Cheers
Rob
I am bringing a different dmm home from work today, so we can see if that was the problem.
I didn't have much time this morning, but I quickly tried to trace a + speaker terminal...
It headed off to the speaker selector (A, B, A+B). I don't really know how the various pins work, but... let's get crazy... and assume that the colors stayed consistent (I was tracing a yellow wire from the speaker +), and indeed there is a yellow wire that leaves the selector and heads for... 1 of those 2 large caps that are side by side (35v 1000uf if I remember correctly).
I am going to re-check some voltages tonight w/ the other DMM, I will let you know what I find
I didn't have much time this morning, but I quickly tried to trace a + speaker terminal...
It headed off to the speaker selector (A, B, A+B). I don't really know how the various pins work, but... let's get crazy... and assume that the colors stayed consistent (I was tracing a yellow wire from the speaker +), and indeed there is a yellow wire that leaves the selector and heads for... 1 of those 2 large caps that are side by side (35v 1000uf if I remember correctly).
I am going to re-check some voltages tonight w/ the other DMM, I will let you know what I find
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