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Old 8th July 2008, 03:33 PM   #11
nigelwright7557 is offline nigelwright7557  United Kingdom
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You really shouldnt be blowing any fuses if you follow a logical testing procedure.

1/ Test transformer on its own.
2/ Check bridge rectifier for shorts
3/ Check power supply caps for a short.
4/ Check output transistors for a short.
5/ Check driver board for shorts.

I would then leave the output transistors disconnected and fire up the driver board with the output fed back into the LTP.
I would set the bias to a minimum.
Once I am convinced the driver board is OK would I consider reconnecting the output transistors.
PCBCAD51 pcb design software. 2018 version out now. http://www.murtonpikesystems.co.uk
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Old 8th July 2008, 04:55 PM   #12
andry1 is offline andry1  United States
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Oh, I'm not blowing any fuses anymore (not sure if you were responding to my last message or not). Corrected a minor wiring SNAFU that was causing the original fuse blowage -- took me about two minutes to do after I got back from Radio Shack last night with my big bag full o' fuses (of which I only needed one).

Amp works fine now, no fuses blowing, pretty glowing tubes on top, etc. I'm just only getting output from one channel due to some "icky" wiring on the RCA input jacks.

Should take me about two seconds to fix, just didn't feel like popping the tubes out again last night to flip it over and correct it since I wanted to get around to installing/aligning the new phono cartridge that arrived yesterday .

Was just thinking about rewiring some or all of the audio signal paths using CAT5 instead of the 'shielded audio wire' that came with the kit, which I'm not overly fond of for various reasons.

I'm sure it will shock all of you to hear that this is the first time I've built one of these things, so I was curious if there was any particular reason why I shouldn't swap the internal audio wiring with CAT5. I can't see any reason why it wouldn't work just fine, but hey, I have been known to be wrong once or twice before
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Old 9th July 2008, 12:52 AM   #13
gingertube is offline gingertube  Australia
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Location: Adelaide South Oz
I've used individual wires pulled from Cat 5 cables for audio signal wiring in SS amps but haven't tried it in a tube amp. You have to be very carefull about wire routing, crossing wires at right angles etc to avoid hum pickup AND occassionally you will find a particular signal line that just has to be done with shielded cable. If you are using Cat 5 wires from the RCA Input connectors to the 1st tube then twist the signal and the 0V wires together, 3 to 5 twists per inch.

There are 2 grades of Cat 5 cable - one (the cheap stuff) has PVC insulated wires, the better grades have teflon insulation. It is this latter one you want to use.

For my tube amp builds, most times now I use thin tinned copper wire which I pass down the centre of some teflon tubing for these feeds. This is much the same thing.

I've listened to some speaker cables made up of multiple Cat 5 wires plaited together. I did'nt care for them that much but some others have "raved" about them.

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Old 9th July 2008, 02:15 AM   #14
Ty_Bower is offline Ty_Bower  United States
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I thought the "problem" with using shielded speaker cable was its inherent capacitance (per inch). It ends up being in parallel with the input, and shorts a small amount of high frequency material to ground. The high frequency roll-off you get might vary if you have a voltage divider on the input (a.k.a., the volume pot). You're better off if you keep the total impedance of the volume pot small (use a 100k pot instead of a 500k) and keep the shielded wiring as short as possible.

Am I mistaken?
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Old 22nd January 2009, 06:48 PM   #15
DaOwart is offline DaOwart  United States
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I also orderd the lighthouse electric sta-45 and also found that more than half of the parts were not the same as the parts list. This was the first tube amp kit that I had built. I couldnt ever get to work...only a faint sound that you could hardly hear. It will make a nice paper weight until I can get some help with it.
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Old 22nd January 2009, 07:17 PM   #16
DaOwart is offline DaOwart  United States
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oh...by the way, how does it sound?
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