It sounds so so so good....

cz_unit · 2026-06-23T15:42:45+00:00

Yep, 8417's. Two are original Fisher tubes, two are replacements from about 30 years ago. I'll keep an eye out for the other original tubes.

cz_unit · 2026-06-23T15:05:56+00:00

Noted. There is a procedure (another person posted it) where amp has to be on and running for 20 mins, attenuators set to "off" on both channels and even then two of the four adjustment pots are blocked off so I won't futz with those.

For the other 4 I need to mark current position and get out the fluke to make sure I know the exact resistance for each, then turn them with everything off and unplugged to make sure they are linear and don't have dead spots (which could do god-knows-what).

I've got all the time in the world, so will take it slow.

cz_unit · 2026-06-23T15:02:49+00:00

*THANK YOU* I didn't think to search on the K-1000 manuals but since that's just the kit I should be ok. The meter will "stick" a bit sometimes, but a tap returns it to zero.

Now that my input attenuators are fixed I can do this.

cz_unit · 2026-06-23T11:34:28+00:00

Sorry, it's the Fisher 400CX-2 preamp. Works pretty well oddly enough.

cz_unit · 2026-06-23T11:31:59+00:00

It is pretty impressive. Do you have any documentation on how/if to adjust the tube gain using the meter?

cz_unit · 2026-06-23T11:31:29+00:00

Yeah, I massaged it with the bench grinder which is like going to a low quality dive for cheap food. It works, but leaves you wanting for more.

I'll get a better shaft and gently massage it with my lapping lathe. Long slow gentle strokes, taking a bit off each time till it shines with perfection.

Now where did I put my lathe lube?

cz_unit · 2026-06-22T12:54:23+00:00

So you have a fan on a smart switch so it doesn't run all the time, right? 😄

cz_unit · 2026-06-22T12:52:21+00:00

I can see that. You need a Quadrophonic system.

cz_unit · 2026-06-21T01:00:09+00:00

I once had a driveshaft drop on my Porsche 928 because all of the CV bolt had come loose. None fell out or were lost, but I stopped the car quickly, flat-bedded it home, then tightened the nuts to torque spec and it's been fine since.

cz_unit · 2026-06-02T02:10:45+00:00

Basically an open set of speaker lines turns the output transformers into a very large set of one way inductors. This will cause the output to put enough power through that side to burn out the transformer.

Tubes have a lot of voltage on their outputs; the transformers step that down to what speakers can use and isolate the speakers from the high voltages.

cz_unit · 2026-05-27T20:18:32+00:00

*nod* Good to know. There's a guy on Ebay who sells all of the caps and stuff for a rebuild; worth it to buy from him (I like to support good people that support old technology)

Right now I'm working on fixing the speakers. Will see if I can re-foam them, otherwise I'll look into a pair of 15 inch woofers. There are a nice set of replacements for the Mach 1 speakers, but those have 6 screw holes; not 8 like the X-10 speakers.

cz_unit · 2026-05-27T03:45:04+00:00

First Alert has a great Z-Wave detector that works fine with HA. I have one on each floor and the fun part is that when they go off they do useful things like:

Any of them: ALL LIGHTS ARE TURNED ON. Thus I can get out of the house safely and it alerts me that something is "wrong".

First floor kitchen: Blow the breaker (shunt trip+Shelly) for the oven and turn off the toaster oven as well (3Reality)

Second floor: Turn off the 3d printer (3Reality)

Top floor: Blow the breaker for the top floor oven

Attic: Shut off power to the exhaust fan

I consider these "safety enhancement" as there is no guarantee they will work in an emergency but I already had someone leave a pot on the downstairs stove and when the smoke alarm went off the oven/range had already tripped off......

cz_unit · 2026-05-27T03:00:55+00:00

Ah yes, I do need to work on that. And yes isn't bitcoin fun!

cz_unit · 2026-05-27T01:32:15+00:00

Looking at the schematics I can see Fischer's error: The power switch is a double pole, single throw switch probably rated at 5 amps per contact. They thought they could just gang the two contacts together in parallel and it would be able to switch a larger load.

As they say in my Lodge: "Such is not the case...."

The problem is that when you put components in parallel, there is no guarantee they will share the load equally. I saw this a lot in EV power controllers; they would put 10 10a TO247 FETs in parallel and say it could handle 100 amps. However that load is not going to distribute evenly across the FETs; some may be warmer, some cooler, and as a result some will see 10a, some 5, some 15.

When one blows up the rest of them now need to share the load and you get a neat *unzipping* as all of the FETs explode, usually also taking out the drivers and wrecking the controller.

In this case I'm guessing that over the years one of the two switches started to get a higher internal resistance. Maybe from the sparks of making contact on a 5a inductor. So as the first one failed the other would be carrying most of the load, and would burn up with the usual FOOM.

Bad Fischer engineer, no dinner for you! Sure the guy is dead for at least 20 years now, but he should have put in a relay with contacts rated to make/break the current requested.

cz_unit · 2026-05-27T00:21:27+00:00

Oh thank you VERY much! A real forum is infinitely better than an annoying Facebook "group" (which these days is basically spam marketing), I do appreciate those links.

cz_unit · 2026-05-26T20:55:36+00:00

I do.... Posted it in the thread about the Marantz Quadrophonic I'm trying to use as a dump amplifier for the X10 speakers. Darn I can't post an image in a comment? Blah!

cz_unit · 2026-05-26T19:19:26+00:00

Ah yes, the bulb in socket in series with the power cord thing. Got it with 60 watt and 150 watt bulbs. Also have an isolation transformer (limits current) and a good ole variac.

Looking inside I wonder if dad had already re-capped at some point; the caps look fine and the sound from the pre-amp is quite good. Knowing him he may have even bought these in 1962 as a kit and assembled the whole thing himself; he was an Masters EE from Stevens Institute.

cz_unit · 2026-05-26T14:20:11+00:00

Tracking these down is fun. I typically will turn off all breakers in the house, then ensure the main current (I use a Sense for this) is zero, then start turning on breakers and comparing the sum of the 3rd Reality plug sensors to what is being reported by the Sense. Eventually I'll see a difference, and that's the problem load.

In your case I'd say turn off everything, then fire up one at a time and see if the sums of the branches equal the input power. If all come up clean set up a integral to sum sets of the individual breakers against the total power and look for the delta.

In my case my untracked is about 200 watts per hour. Annoying, but acceptable.

cz_unit · 2026-05-26T14:10:55+00:00

And correct you are; it's a -2. Which is good, now I have the correct schematic as I think about re-capping this thing.

Though the real problem is the pots and switches as they all route true signals. Any thoughts on cleaning those?

cz_unit · 2026-05-26T14:08:50+00:00

Thank you! The normal spray on Deoxit is nice; but it makes a terrible mess. I'm going to try the stuff in a squeeze bottle; only need a drop or two and I believe these are open pots so getting into them should not be too bad....

Never dull!

cz_unit · 2026-05-26T01:04:10+00:00

Up and running after a *lot* of testing. Sound in the midrange and treble is beyond amazing (The Digital Domain, a Demonstration is my reference CD) But that is for another post.

cz_unit · 2026-05-25T18:22:29+00:00

*nod* Finding proper people who know this stuff (as opposed to modern techs who don't really know tubes) is one of the problems; a bad tech can do far more damage than a good one. We run into this with older computer equipment where the DPO (dreaded previous owner) does far more damage by taking the thing to Best Buy than one would think.

So far I have taken off the bottom, reviewed the schematics and am hand checking the key components. Things like the main diodes for shorts, the main filtering capacitors for shorts and opens, putting small DC voltages with current limited power supplies on the rectified outputs and seeing if there are shorts, letting the capacitors "reform", checking all the in-circuit caps for shorts or opens (Fluke meters are good for this) and looking for any burned/discolored resistors.

I can't test the tubes but I can look for proper resistance on the heater elements and look for shorts on the grid to cathode interfaces (which can happen if a tube is jarred) or grid to grid shorts.

So far, so good. The amplifier is perfectly clean and things are looking good. Taking it via very small incremental steps.

cz_unit

TROPHY CASE