I just bought this Amplifier on ebay recently and it worked for
a short 30 minutes until the primary coil burned out on the output
transformer on the right channel. I purchased a sam's photofact for this amplifier and for the short time I had it running on my Altec mod 14's, it sounded superb. This impression that I had with this amp may be somewhat biased by the fact that I am so
spoiled with using solid state products since the late 60's. This
is a far cry from a Mac or a Mark levinson but I hope to find it worthwhile to restore this amp back to it's new and operational state.
I have the transformer removed and I have examined the burn spot to confirm that the device is indeed burned. It has 3 leads
coming in for primary and 3 for the secondary. I would like to upload some photos of the unit and the photofact to give you a better illustration of this unit.
I have been trying to shop around for a replacement transformer
but the specs and appearance seems to be a lot different and I am afraid replacing the transformers with the wrong specs and doing more harm than good.
From the photofact: each output transformer has the following data: primary:6100 ohm tap @ 30%
From the schematic: 310v primary (blue) (from plate?)
320v pri tap? (brown) (from grid?)
333v pri ? (red)
16 ohm secondary green
8 ohm tap Yellow
com black
The preamp stage has 1 12AX7A
The AF stage has 1 ea 12AX7A (each channel)
Outputs are 1 ea EL84 (each channel)
I suppose the rectifier is EZ81 or 6CA4
a total of 6 tubes
I am trying to establish some sense of what is on the amplifier so taht I may be able to ascertain the approximate output of this amp. This will be instrumental in finding a suitable replacement output transformer.
So My question is in 3 parts.
1) could you be able to guestimate for me the output rating of this amplifier based on the info that I have posted so far?
if so, what is it?
2) What would you recommend in replacing the transformer? 2 new ones or a near match on the old?
3) Is this chassis model worth salvaging or should I find another desighn to restore?
your input would be most helpful. I have some jpegs of the sams and some color photos of the project itself if you will be needing images.
regards,
Allen
a short 30 minutes until the primary coil burned out on the output
transformer on the right channel. I purchased a sam's photofact for this amplifier and for the short time I had it running on my Altec mod 14's, it sounded superb. This impression that I had with this amp may be somewhat biased by the fact that I am so
spoiled with using solid state products since the late 60's. This
is a far cry from a Mac or a Mark levinson but I hope to find it worthwhile to restore this amp back to it's new and operational state.
I have the transformer removed and I have examined the burn spot to confirm that the device is indeed burned. It has 3 leads
coming in for primary and 3 for the secondary. I would like to upload some photos of the unit and the photofact to give you a better illustration of this unit.
I have been trying to shop around for a replacement transformer
but the specs and appearance seems to be a lot different and I am afraid replacing the transformers with the wrong specs and doing more harm than good.
From the photofact: each output transformer has the following data: primary:6100 ohm tap @ 30%
From the schematic: 310v primary (blue) (from plate?)
320v pri tap? (brown) (from grid?)
333v pri ? (red)
16 ohm secondary green
8 ohm tap Yellow
com black
The preamp stage has 1 12AX7A
The AF stage has 1 ea 12AX7A (each channel)
Outputs are 1 ea EL84 (each channel)
I suppose the rectifier is EZ81 or 6CA4
a total of 6 tubes
I am trying to establish some sense of what is on the amplifier so taht I may be able to ascertain the approximate output of this amp. This will be instrumental in finding a suitable replacement output transformer.
So My question is in 3 parts.
1) could you be able to guestimate for me the output rating of this amplifier based on the info that I have posted so far?
if so, what is it?
2) What would you recommend in replacing the transformer? 2 new ones or a near match on the old?
3) Is this chassis model worth salvaging or should I find another desighn to restore?
your input would be most helpful. I have some jpegs of the sams and some color photos of the project itself if you will be needing images.
regards,
Allen
My guess would be that a single EL84 per channel amp would be pushing a max of 6w in class A.
You could plop in a replacement OPT but it may be a real challange matching one to the old one. Perhaps you could buy one and if you don't like the results you could replace the OPT on the other channel too.
Worth restoring? Let me put it this way. You'll probably learn a lot, and you can always mod the circuit to your liking.
You could plop in a replacement OPT but it may be a real challange matching one to the old one. Perhaps you could buy one and if you don't like the results you could replace the OPT on the other channel too.
Worth restoring? Let me put it this way. You'll probably learn a lot, and you can always mod the circuit to your liking.
Unfortunately, that picture is absolutely minuscule and impossible to read. Try www.imageshack.us to host it in full size.
You aren't likely to find an exact replacement. What is hole spacing?
Edcor makes a 8K to 16 Ohm which you could use as 4K to 8 Ohms.
Hammond 125CSE is about the right size, but has no screen tap. And it doesn't have much low end.
Triode Electronics has a guitar amp replacement that will probably fit, but won't have much low end (probably less than the Hammond).
Edcor makes a 8K to 16 Ohm which you could use as 4K to 8 Ohms.
Hammond 125CSE is about the right size, but has no screen tap. And it doesn't have much low end.
Triode Electronics has a guitar amp replacement that will probably fit, but won't have much low end (probably less than the Hammond).
We learn new stuff every day! I was afraid to overload my
jpg allocation and get kicked off! Thanks for the link to
upload images.
Here's the link to to the scanned in version.
http://profile.imageshack.us/user/parvo3/images/detail/#171/picturewa3.jpg
I haven't learned the tiny url thingie just yet but I hope this will work.
regards,
Allen
jpg allocation and get kicked off! Thanks for the link to
upload images.
Here's the link to to the scanned in version.
http://profile.imageshack.us/user/parvo3/images/detail/#171/picturewa3.jpg
I haven't learned the tiny url thingie just yet but I hope this will work.
regards,
Allen
Big transformers for an SE amp... the Hammond 125DSE is that size, as is the Edcor. 50-18K is a LOT to hope for... feedback will improve the response beyond that, though it can't help if you reach transformer saturation at the low end. The Edcor will have the best low end, as it's designed for 8K impedance - using it as 4K will take the response an octave lower.
One other possibility would be to have Electra-Print make you a replacement set.
Are you sure the primary of this output transformer burned out? Can you describe the process you used to make this determination?
How does it differ in terms of dcr from the working transformer? (Is the primary truly open?)
Obviously you need to determine the cause of the failure, presumably that channel's output tube is bad as well, and probably traceable to a bad component. The output stage cathode resistor and bypass capacitor are shared between both channels. (And should be replaced along with the coupling caps and power supply electrolytics)
Are you sure the primary of this output transformer burned out? Can you describe the process you used to make this determination?
How does it differ in terms of dcr from the working transformer? (Is the primary truly open?)
Obviously you need to determine the cause of the failure, presumably that channel's output tube is bad as well, and probably traceable to a bad component. The output stage cathode resistor and bypass capacitor are shared between both channels. (And should be replaced along with the coupling caps and power supply electrolytics)
I presumed the arcing and sparks coming from the bottom of the transformer would be the tell-tale problem as there is a large burn spot on the area where the B+ wire extends from the primary winding side. after snipping leads and removing the
transformer I took the following readings. The primary side has three wires, red B+,brown screen tap, and blue.(other side of the primary) Taking a reading from the tap and B+, I get 174 ohm.
between the B+ and the blue, 22kohm and the tap and blue is 22K ohm. I'd have to assume that the winding between the
B+ and screen tap has eroded.
I checked all the tubes individually twice on my Mercury tube checker for shorts (none) and opens (none) and they all tested
at least 80 percent. Now my EICO in circuit capacitor checker
is still being studied and I have to learn to use it before I can make any judgements on the coupling caps or the others.
I am sure there are some that need replaced by virtue of their
ripe age.
I hope this clarifies the condition of the transformer in question.
I realize that those vintage caps (spragues may need some looking at and perhaps I should just get a redesign on the circuit board by usingelectronic workbench and modernize it's
circuitry and replace all those old caps with new electrolytics.
I sure would like to restore it to see if will sustain by it's original
design.
I really appreciate all the input and help. meanwhile my quest for
transformers continue.
regards,
Allen
transformer I took the following readings. The primary side has three wires, red B+,brown screen tap, and blue.(other side of the primary) Taking a reading from the tap and B+, I get 174 ohm.
between the B+ and the blue, 22kohm and the tap and blue is 22K ohm. I'd have to assume that the winding between the
B+ and screen tap has eroded.
I checked all the tubes individually twice on my Mercury tube checker for shorts (none) and opens (none) and they all tested
at least 80 percent. Now my EICO in circuit capacitor checker
is still being studied and I have to learn to use it before I can make any judgements on the coupling caps or the others.
I am sure there are some that need replaced by virtue of their
ripe age.
I hope this clarifies the condition of the transformer in question.
I realize that those vintage caps (spragues may need some looking at and perhaps I should just get a redesign on the circuit board by usingelectronic workbench and modernize it's
circuitry and replace all those old caps with new electrolytics.
I sure would like to restore it to see if will sustain by it's original
design.
I really appreciate all the input and help. meanwhile my quest for
transformers continue.
regards,
Allen
Eric 3460P = Soundcraftsmen 2020 tube integrated amp
The Soundcraftsmen model 2020 integrated amp uses the same circuit and it's a great sounding amp. It only sounds good working in tandem with the line-stage and tone control. Smooth and punchy. Do NOT underestimate it. Great sound!
I've tried to use just the amp section and it changed the sound from full to anemic and thin, smooth to grainy. The tone control can possibly eliminated but the line section and "loudness" should be intact. I believe this amp sound and tone were voiced or designed with the preamp in mind. Proceed with care so you won't ruin the sound like I did. I need to restore the amp/ sound to its former glory.
Here's a schematic that's cleaned up, simplified, and minus the phono section:
.
Reposting original schematic:
.
Comparison between Eric 3460P and Soundcraftsmen 2020.
.
The Soundcraftsmen model 2020 integrated amp uses the same circuit and it's a great sounding amp. It only sounds good working in tandem with the line-stage and tone control. Smooth and punchy. Do NOT underestimate it. Great sound!
I've tried to use just the amp section and it changed the sound from full to anemic and thin, smooth to grainy. The tone control can possibly eliminated but the line section and "loudness" should be intact. I believe this amp sound and tone were voiced or designed with the preamp in mind. Proceed with care so you won't ruin the sound like I did. I need to restore the amp/ sound to its former glory.
Here's a schematic that's cleaned up, simplified, and minus the phono section:
An externally hosted image should be here but it was not working when we last tested it.
.
Reposting original schematic:
An externally hosted image should be here but it was not working when we last tested it.
.
Comparison between Eric 3460P and Soundcraftsmen 2020.
An externally hosted image should be here but it was not working when we last tested it.
.
I recently simplified the circuit further and it sounds great. Singled ended 6BQ5 can be amazing!
.
An externally hosted image should be here but it was not working when we last tested it.
.
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