Hey all!
I have an old carver tfm-15 cb that is fried. The meters are still good, the transformer and power supply are still great but the amp board is cooked.
I'm thinking about gutting this thing and putting in a couple of Naim 140 boards. After some measurements it looks like it will fit with lots of room to spare. The heat sinks are plenty big enough and it should work out.
The question I have is about the transformer, the only literature I can find on the 140 boards is that it takes +/- 40 volts. My transformer puts out 40-0-40 and the psu bumps it up to 53-0-53 DC. Now I'm sure I'll have to replace the psu or at least tone it down. But does the Naim 140 take a rectified 40-0-40 or rectified 20-0-20?
can anyone help me out?
Thanks guys
mark H.
,
I have an old carver tfm-15 cb that is fried. The meters are still good, the transformer and power supply are still great but the amp board is cooked.
I'm thinking about gutting this thing and putting in a couple of Naim 140 boards. After some measurements it looks like it will fit with lots of room to spare. The heat sinks are plenty big enough and it should work out.
The question I have is about the transformer, the only literature I can find on the 140 boards is that it takes +/- 40 volts. My transformer puts out 40-0-40 and the psu bumps it up to 53-0-53 DC. Now I'm sure I'll have to replace the psu or at least tone it down. But does the Naim 140 take a rectified 40-0-40 or rectified 20-0-20?
can anyone help me out?
Thanks guys
mark H.
,
The original Carver supply voltages are +52VDC and -52VDC.
The Naim supply voltages should be +40VDC and -40VDC.
This requires a secondary winding of 56VAC center tapped,
or 28VAC-0-28VAC. Or, two 28VAC secondaries, connected
in series to form a single winding with a center tap.
Your right 52 not 53
So can I rectifie my center tap 40-0-40 Trans to put out the +40/-40 required?
So can I rectifie my center tap 40-0-40 Trans to put out the +40/-40 required?
You may be able to use it with a choke input type supply circuit.
That would give about +36VDC/-36VDC.
But a dual secondary toroid is not too expensive, and is available
with 30VAC dual secondaries. That may be the best way to go.
Avel Lindberg Y236802 500VA 30V+30V Toroidal Transformer
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Thanks for that info, I'll look into that. I was just hoping to save 50 bucks but it sounds a lot more complicated putting in chokes than just replacing transformer.
it sounds like you've built a few amps, how does a 140 sound and do you think it might be OK with bose 901s?
it sounds like you've built a few amps, how does a 140 sound and do you think it might be OK with bose 901s?
The Naim should be fine for your system. Have you built an amp before?
Do you have any test equipment?
One thing you could do instead is use a bucking transformer coupled with the original
Carver transformer to lower the supply voltage. You'd need a small 120VAC/30VAC
transformer, with 5A secondary rating. The primary goes in parallel with the 120VAC line,
and the secondary would be connected in series with the Carver primary, in the correct phase,
which would reduce the effective input voltage by 25%. This would give the needed +40/-40 VDC.
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With adequately-rated parts there is no problem running the Naim circuit on your original rails of c. +/-53v.
Pushing a clone pcb/kit that far is a total crapshot though!
Pushing a clone pcb/kit that far is a total crapshot though!
I have noticed that many of the Chinese boards have power ratings that are just under the board's capacitor's ratings, and could operate at higher voltages when those parts are replaced.
As mentioned above, I would tend to be very cautious, however!
As mentioned above, I would tend to be very cautious, however!
Hey folks , thanks for the advice.
I've never built a complete amp before. After what I call bad advice from another site, I blew my carver m-1.5t to pieces. So my first experience in amp building was 1st learning how to read schematics then figuring exactly what each component was and did. Taught myself how to make pcbs, restuffing them putting it all back together, plugging it in, watch more sparks fly then starting over. After 4 months of that I finally got this thing mastered and it sounds better than it ever did and drives my 901s with a LOT of authority. A friend of mine Oscoped it at the local C.C. and the teacher couldn't believe how clean the signal was. (I don't know what that means)
I bought the tfm-15 from flea bay as a perfectly working until I plugged it I to to the rest of my stereo while my 1.5t was down and BAM BAM! Smoked two drivers and started a fire in the wall of my house (I have a built in rack) not very happy with my purchase.
tools I baught, triac (after the first 2 tries failed) very nice solder station, 3 different fluke DMMs, cap tester,diode tester, Trans tester, I bought a cheap O scope but I don't know how to use it. I guess I still need a signal Gen and some dummy loads.
the other amp I'm looking at is the symasym 5.3 but I think the boards might be too big for what I want to do.
I've never built a complete amp before. After what I call bad advice from another site, I blew my carver m-1.5t to pieces. So my first experience in amp building was 1st learning how to read schematics then figuring exactly what each component was and did. Taught myself how to make pcbs, restuffing them putting it all back together, plugging it in, watch more sparks fly then starting over. After 4 months of that I finally got this thing mastered and it sounds better than it ever did and drives my 901s with a LOT of authority. A friend of mine Oscoped it at the local C.C. and the teacher couldn't believe how clean the signal was. (I don't know what that means)
I bought the tfm-15 from flea bay as a perfectly working until I plugged it I to to the rest of my stereo while my 1.5t was down and BAM BAM! Smoked two drivers and started a fire in the wall of my house (I have a built in rack) not very happy with my purchase.
tools I baught, triac (after the first 2 tries failed) very nice solder station, 3 different fluke DMMs, cap tester,diode tester, Trans tester, I bought a cheap O scope but I don't know how to use it. I guess I still need a signal Gen and some dummy loads.
the other amp I'm looking at is the symasym 5.3 but I think the boards might be too big for what I want to do.
Apologies for reviving such an old thread but I'm looking for a replacement meter for an otherwise good working Carver TFM-15 so just wanted to ask if you ever did anything with this amp or is it still sitting on a shelf?
Thanks,
Scott