No power. (continued from PP)

[Bryce]

Considering the latest escapades over on that forum (and the sure-to-be-gestating ban for arguing with certain people...! haha), I figured I'd move this over here... continued from this thread.

Finally got the probes in. I'm guessing the Mains switch has gone bad, as the readings from the bulgin plug are fine (err, within reason, our AC runs a tad hot in this building, I suppose: 120VAC). Before the switch, voltage is fine, measures 120VAC. Measuring after the switch I get 40VAC with the mains switch "off," with it "on" I get no reading whatsoever. This also confirms my readings from the AC mains selector: 40VAC with the mains switch off, no reading with it on.

Bad switch?

I also noticed that the caps are starting to get those lovely little bulges. Guess it's time. I take it this is the kit chosen by experts the world over?

[mhuss]

How are you measuring these? I suggest one lead on the chassis, and the other tracing the voltage at each point from the mains input on.

--mark

[OldSchoolDave]

You're always welcome here, you argumentative cuss !

To verify the switch is the issue, you could CAREFULLY jumper the contacts (with the mains cable removed, of course), then connect the mains cable and see if your amp springs to life.

Replacement switches are available on VHR. How long ago did you have your amp recapped?

Dave

[Bryce]

Mark,

First I measured the "off" positive/neutral terminals on the Mains switch to establish that she was even getting power. Then moved to the "on" terminals which gave me 40VAC with the switch in the "off" position and 0VAC with it in the "on" position - I just double-checked this and I'm getting absolutely nothing now (on the "on" side with the switch either on or off).

With the negative probe clipped to chassis/ground I was getting 120VAC with neutral at the bulgin, Mains On/Off and at the Mains selector. I didn't test beyond that, as when I tested for hot I was getting nothing at any of the above locations. In fact, clipping neg to the bulgin's ground and measuring for hot gives me nothing, either.

If I am missing something simple here smack me. If I wasn't going to get a reading from x to ground, wouldn't it be neutral, not hot? Shouldn't I at least get a reading straight away at the bulgin?

Dave,

I'll have to go through my receipts but she was first serviced by my tech Jim in early 2004 (January? Sorry, long time ago!). I swear she was recapped then but it wouldn't make any sense to have the caps failing now. Maybe it was the Laney that got the cap job, not the Hiwatt. I'll find out.

I might just try jumpering the contacts to see if there's an issue, but I'll wait for Mark to chime in on the above. Have to verify that I'm not completely "slow thinkin'" before I whip out some wire.

Thanks for your help, guys!

Bryce

[Dr.HI-TONE]

Bryce, you are certainly welcome here!

That is the kit, if the shipping turns out to be to high, I refund the difference. So don't worry too much!

[OldSchoolDave]

... in early 2004 (January? Sorry, long time ago!). I swear she was recapped then but it wouldn't make any sense to have the caps failing now.

Exactly what I was thinking. The caps should have date codes (usually in year-month format - see: http://mhuss.com/Hiwatt/dates.html ). Five year old caps shouldn't be bulging...

Dave

[Bryce]

Oldest caps on the Hiwatt: '73. Youngest: 47th week of '75. Guess that answers that!

[OldSchoolDave]

Guess that answers that!

Yup! Amazing how time flies...

I see a recap kit and mains switch in your future .

Dave

[Bryce]

All right, I've finally got around to chasing this ghost.

The mains switch now works - or always worked and I was just doing it wrong (likely). Still, regardless, it is on my list to replace. Even so, with mains on the 'on' bulb never lights. Reading the schematic (correctly?) leads me to believe that this won't affect operation, and is most likely because of the fact that...

There is no voltage passing through the mains fuse (I've tried this with both 6A and 5A fasts I've got). As in, if I measure from where mains brown enters the fuse holder to neutral, I get a reading. If I measure after the voltage should have passed through the fuse holder (the little metal clip on the top) to neutral then I get no reading at all.

So, barring the fact that I am a complete and utter idiot (which is extremely likely, I guarantee), this leads me to believe that my fuse holder has gone bad.

If you guys agree to this then I'm glad to report that I'll FINALLY pop off to VHR and buy this stuff so my Hiwatt can shake the grounds once again.

Thanks, guys.

Bryce

[mhuss]

That's really odd. I can't remember ever having a fuse holder just fail. Broken, lots of times, but physically good and not passing current, never.

When the power has been off for at least 10 minutes, try measuring the ohms across the two fuse terminals with the fuse in.

--mark

[Bryce]

Hey Mark,

I get no reading whatsoever. Absolutely zero, the needle doesn't even flicker. To be sure I measured across HT - works fine.

I even pulled the top off the fuse and used one of the leads to push the fuse as far into the holder as it would go and got no reading at all. Reading between the outer end of the fuse and its terminal - good. Reading between the two terminals or the outer end of the fuse - nothing.

Thanks!

Bryce

[Bryce]

Please file this under the "complete and utter dumb@#$" file, would you?

Two years later I do the unthinkable - pull the fuse out and shine a flash light into the holder to see if, over the course of thirty+ years, some gunk or dust or crap might have worked its way in-between the fuse and its connection. Sure enough. Blow the majority out and pick out the rest. Plug her in, she lights up and sounds gorgeous.

You all have my full permission to ridicule me at the next convention.

Bryce

[OldSchoolDave]

You all have my full permission to ridicule me at the next convention.

This, of course, means you are obligated to attend .

Glad to hear it was a simple remedy. Serves as a good reminder for us all to always check for physical impediments before moving onto deeper troubleshooting.

Dave

[mhuss]

+1. Gunk, dust and corrosion take their toll on amps that are 30+ years old, and have spent most of their lives in dirty environments and/or in the back of a truck.

--mark