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Offset problem with TFM-55?

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BillD

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(pair of) SILVER-7 TUBE AMPs

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Post Sun Nov 02, 2008 2:54 pm

Re: Offset problem with TFM-55?

Rich, wouldn't substituting that 1µF coupling cap just reduce the corner frequency by about a half? That wouldn't be a bad thing, or is it somehow interrelated to another circuit.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
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Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer
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RichP714

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Post Sun Nov 02, 2008 3:58 pm

Re: Offset problem with TFM-55?

BillD wrote:Rich, wouldn't substituting that 1µF coupling cap just reduce the corner frequency by about a half? That wouldn't be a bad thing, or is it somehow interrelated to another circuit.
Yes, it would bring it down by about half; not devastating; it would still block DC, just a bit higher cap than the spec.

BTW, brit, I saw in the other thread that you were asking about discharging caps.

The problem some techs have with blowing mag coils has nothing to do with discharging caps, it has to do with trying to 'jump start' the power supply by shorting across the triac. That will destroy the magnetic coil.

Discharging large value power supply caps is good practice, and bill's lightbulb idea is a nice, safe way to do it if you want to reuse the cap. If you are going to trash the cap anyway, you CAN just short across its terminals with a jeweler's screwdriver that has a plastic handle to insulate your hand.

The power supply caps circuit has small bleeder resitors to drain them after a couple of minutes of being unplugged. As long as those bleeders are intact, they should be drained to ground after a couple of minutes anyway, but it's nice to be safe about things.
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BillD

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Post Sun Nov 02, 2008 4:12 pm

Re: Offset problem with TFM-55?

I have a suspicion (it's just that) that my Sunfire power amp uses the bulb in the meter to discharge the caps. When you power it off (via the trigger), the light goes out then comes back on again for a few minutes) After about 15 minutes, it's off (I've never sat around and watched and timed how long it takes). I've applied a signal to the amp while the lights are still on, and got nothing (the amp was truly off).
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer
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brit01

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Post Sun Nov 02, 2008 4:12 pm

Re: Offset problem with TFM-55?

BTW, brit, I saw in the other thread that you were asking about discharging caps.

The problem some techs have with blowing mag coils has nothing to do with discharging caps, it has to do with trying to 'jump start' the power supply by shorting across the triac. That will destroy the magnetic coil.

Discharging large value power supply caps is good practice, and bill's lightbulb idea is a nice, safe way to do it if you want to reuse the cap. If you are going to trash the cap anyway, you CAN just short across its terminals with a jeweler's screwdriver that has a plastic handle to insulate your hand.



cheers Rich, yes I picked up on the difference there. I used the light bulb but the caps were well drained over night and had no effect on the light bulb.

I took them out successfully and placed the new ones in. Just got to wait for the 35V 6800uF caps to arrive. Maybe this week.

I'm also fishing around for the diodes, transistors (2SC3467) and the trimmer pots in the UK. bit complicated as some have minimum orders like Digi-Key, some out of stock, some high shipping costs ](*,) ](*,) ](*,)
TFM-55, CT-3, Klipsch F-1, Rotel RCD 930AX
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BillD

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(pair of) SILVER-7 TUBE AMPs

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Post Sun Nov 02, 2008 4:13 pm

Re: Offset problem with TFM-55?

What, you don't want 1000 ea. trimmer pots?
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer
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RichP714

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Post Sun Nov 02, 2008 4:33 pm

Re: Offset problem with TFM-55?

you could always make a necklace out of the extras ;)
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brit01

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Post Sun Nov 02, 2008 4:34 pm

Re: Offset problem with TFM-55?

What, you don't want 1000 ea. trimmer pots?


I always wanted to start my own business. RS components have a min order of 250 for the FDH400 diodes 8-[
I could put Carver back into production :^o
TFM-55, CT-3, Klipsch F-1, Rotel RCD 930AX
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BillD

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(pair of) SILVER-7 TUBE AMPs

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Post Sun Nov 02, 2008 4:40 pm

Re: Offset problem with TFM-55?

They're available from Mouser by the unit.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer
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brit01

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Post Sun Nov 02, 2008 4:48 pm

Re: Offset problem with TFM-55?

They're available from Mouser by the unit.


Thks Bill but the pound/dollar exchange rate now will kill me. Was great 2 months ago but now anything in USA will cost me 30% more :( :( :(
TFM-55, CT-3, Klipsch F-1, Rotel RCD 930AX
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brit01

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Post Sun Nov 02, 2008 5:06 pm

Re: Offset problem with TFM-55?

Can the fast recovery diodes (FR603) age like caps? Or do they just work or fail?

Just considering changes all of them due to the prices of them.(was planning on just replacing 8 of them, 4 on each channel.

I can get a 25 pack for 6.50 GBP (plus 10 GBP shipping!!). Otherwise I'm paying 89 pence each one from another supplier down the road from my parents house.
TFM-55, CT-3, Klipsch F-1, Rotel RCD 930AX
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BillD

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(pair of) SILVER-7 TUBE AMPs

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Post Sun Nov 02, 2008 5:20 pm

Re: Offset problem with TFM-55?

brit01 wrote:
They're available from Mouser by the unit.


Thks Bill but the pound/dollar exchange rate now will kill me. Was great 2 months ago but now anything in USA will cost me 30% more :( :( :(
I'm sure that at 7¢ apiece, the exchange rate wouldn't kill you. You might try BAV20 as a substitute.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer
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brit01

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Post Sun Nov 02, 2008 6:32 pm

Re: Offset problem with TFM-55?

'm sure that at 7¢ apiece


7 cents for Fr603?
57 cents I see at mouser. Still a very good price for just 1 item.
How much is their shipping? I would need a sponsor to send me the items as a 'gift'.8-[ 8-[



Let me check things out further.
TFM-55, CT-3, Klipsch F-1, Rotel RCD 930AX
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RichP714

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Post Sun Nov 02, 2008 7:05 pm

Re: Offset problem with TFM-55?

brit01 wrote:Can the fast recovery diodes (FR603) age like caps?......
No
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RichP714

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Joined: Fri Oct 12, 2007 2:12 pm

Post Sun Nov 02, 2008 7:07 pm

Re: Offset problem with TFM-55?

brit01 wrote:
'm sure that at 7¢ apiece


7 cents for Fr603?
57 cents I see at mouser. Still a very good price for just 1 item.
How much is their shipping? I would need a sponsor to send me the items as a 'gift'.8-[ 8-[



Let me check things out further.
If you need FR603's I can send you some
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BillD

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Post Sun Nov 02, 2008 7:41 pm

Re: Offset problem with TFM-55?

I was talking about FDH400
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer
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