Hiwatt DR103 voltage problem on new build

[dvlp]

Are you sure read corectly 4mV over 1 ohm resistor?

I thought of that too. They measure right at 1 ohm.

[Jazz P Bass]

How about backing off to the 'coolest' bias setting (ie: most negative) & see where that leads.

I just worked on a Blackstar 100 that the factory biases there EL34's at 25mv's per tube.
Yeah, it had a touch of crossover distortion but it sounded awesome.

[dvlp]

38mV tube bias
-38v bias voltage
464 plate voltage

I figured out what was causing the heavy load. I used a 250 watt light bulb current limiter on my initial startup and left the amp plugged into it just to be safe. Unplugged the limiter and the problem seems to have vanished. I can't believe it was something that simple. I've been racking my brains for days on this.

I appreciate everyone trying to help. Thanks

[Jazz P Bass]

One of the most misused tools.

[Justin Thomas]

But better overused than not at all, maybe?

How does one choose the appropriate light bulb for the application? I've been using a bulb that is as close as reasonably possible to the expected power output of the amp - meaning 30W, 60W, 100W for most of what I work on... No need for a 200W bulb on a 20W amp, right?

Justin

[dvlp]

How does one choose the appropriate light bulb for the application?

I took the advice from a guy that goes by Uncle Doug on youtube. If you search "current limiter" you should find his video. He says any tube amp should use 200w+ because the lower resistance reduces the effect it has on your voltage. That's using 120v at the wall. Obviously 250 watt bulb still had a big effect on my 100 watter. On solid state he said you can get away with 40 watts. I bought the 250 watt photo lamp he suggested. It's a pretty compact size for the wattage.

If you search eBay for "EIKO PH 213 ENLARGER BULB" there's guy selling them for $5 with free shipping

[Enzo]

But voltage readings in the circuit are not legitimate anyway with a bulb. The bulb is used to save the amp from blowing fuses. Once the amp is no longer drawing excess current, we get rid of the bulb. If you use a giant 200 watt bulb, it offers way less protection to your amp than a 60 watter would. It is not intended we operate the amp in a meaningful way while on the bulb.

[catalin gramada]

I took the advice from a guy that goes by Uncle Doug on youtube. If you search "current limiter" you should find his video. He says any tube amp should use 200w+ because the lower resistance reduces the effect it has on your voltage. That's using 120v at the wall. Obviously 250 watt bulb still had a big effect on my 100 watter. On solid state he said you can get away with 40 watts. I bought the 250 watt photo lamp he suggested. It's a pretty compact size for the wattage.

If you search eBay for "EIKO PH 213 ENLARGER BULB" there's guy selling them for $5 with free shipping

Uncle Doug is a cool guy. Rusty is too fat still.

[Mick Bailey]

A 250W bulb on 120v? That's way over what I would use. That means the amp can pull just over 2A on the primary, so provide a secondary current that's easily capable of causing damage in a tube amp. In some ways it's worse than plugging the amp straight into the mains and the fuse blowing.

[g1]

Agree with Mick. I'm not sure what Uncle Doug is trying to achieve using the big bulb.
He is going to a higher wattage to avoid the bulb doing it's safety 'thing', which kind of defeats the whole purpose?
We had the same discussion on another forum and one of the members mentioned it to him. I guess he either didn't understand or didn't care.
I've kind of had a 'dim' view of his vids since then.

[DrGonz78]

The Uncle Doug light bulb limiter lamp wattage issue has come up before over on SSguitar.com.
https://www.ssguitar.com/index.php?t...28301#msg28301

In that instance Uncle Doug did add a note on his video about using 100 watt or lower bulbs on Solid State type amps after being made aware of the SSguitar.com thread. The problem with doing just a note on the video is that not everyone is going to see those notes. For example, when I watch youTube these days it is through my Roku player right into my TV in the living room. You do not get notes appended to the video and if I was learning about light bulb limiters that way then I would not see the warning note he added. Also, that note says 200+ wattage bulbs for tube amps and I don't agree with that either, nor does the community here. Even then he starts the video out saying... "The larger the wattage the better." Personally I think that Uncle Doug video should be removed as it causes way too much confusion.

[J M Fahey]

Some of Uncle Doug´s advice is dubious or iffy; this is one example.

[Randall]

I currently (see what I did there) have a 100 watt industrial bulb in my limiter because I thought it was better than the 60 watt I had in there before. What is the consensus on that?

[Justin Thomas]

Something in me just always said, use the closest sized bulb to what the expected trace the amp would draw from the wall... there's a little label, usually by the fuse that us "fuse size," and then "### WATTS," usually the expected audio output power plus 60-100%... So I usually am using a 60W bulb, with 150 for 100W amps...

Justin

[Leo_Gnardo]

Some of Uncle Doug´s advice is dubious or iffy; this is one example.

But the dog never fails. I just encountered a power transformer that would throw ol' Rusty into a sneezing fit. Roasted like a weiner that fell thru the barbecue grill, no point in trying to use it.