Tube shield in a Hiwatt?

[hulakatt]

Lurked wayy too long before finally digging in here. Built several amps over a few years and haven't built one for awhile so I'm digging back in and building my first Hiwatt!

Anyway, currently building a dr504 and was wondering how important that heat shield between the power tubes and the cap cans is? If I leave it out, will the power tubes melt the cans or does it just take the edge off? I suspect it's more significant on the dr103 than the dr504? Anyone run a dr504 without that tube shield? Any issues?

[jabguit]

I always thought it was for shielding EMI, not heat.
Maybe I'm wrong though......

cheers

[martin manning]

I'm going with IR reflector/convection baffle.

Hulakat, you must be aware of M Huss' site. Scroll down and see under "Heat Shield" https://hiwatt.org/DIY/ I would definitely try to find something to put in there.

[hulakatt]

I'm going with IR reflector/convection baffle.

Hulakat, you must be aware of M Huss' site. Scroll down and see under "Heat Shield" https://hiwatt.org/DIY/ I would definitely try to find something to put in there.

I've been through that site, I was looking for slightly more info than "this is what it looks like". I can put it in, I was just wondering how important it was and what function it actually served.

[martin manning]

Mark Huss checks in here from time to time, maybe he can comment on the benefits of the plate.

[Dr Tony Balls]

I'm going with IR reflector/convection baffle.

Hulakat, you must be aware of M Huss' site. Scroll down and see under "Heat Shield" https://hiwatt.org/DIY/ I would definitely try to find something to put in there.

I've been through that site, I was looking for slightly more info than "this is what it looks like". I can put it in, I was just wondering how important it was and what function it actually served.

I've built a few Hiwatt style without them and never noticed anything lacking, FWIW.

[martin manning]

I'm thinking that baffle will help keep the temperature inside the head cab down.

[gldtp99]

I built two DR504 clones in 2006 without heat shields ---- One I still have and it is still running fine --- The other was sold to a touring band that has been using it since then playing all over the SW USA, Mexico, and parts of South America --- They brought it back to me once for a "tune up" and new tubes ---- I cleaned it up, installed new tubes, tested it ---- The owner tested it and told me, "We'll see you again in ten years or so"

I built my last DR103 clone in 2021 and used a heat shield because I had a few on hand

Either way, it doesn't seem to effect the performance of the amp as far as I can tell

I've also built Hiwatt type clones with the Filter Cap cans mounted inside the chassis along the side chassis rails (something like the Hylight PCB models) ---- One DR103 clone is lent out to my friend's band as a bass amp ---- It's still going strong

Here's the Touring Band that has the DR504 clone I built in 2006 (It's the white tolex head sitting on top of the Orange 4x12 cab):

https://www.youtube.com/watch?v=nvsrvFUsqmw

[chaccmgr]

Electrolytics can and will dry out. This is accelerated by external heat. The degradation of Electros is gradual, so there is no instantaneous failure, they just get worse over time without noticing until they either fail or the amp gets noisy. All amps need a cap job from time to time. My tube bass amp (similar topology to Hiwatt) is currently experiencing bad caps after 12 years and I used the heat shield.

The primary purpose of the shield is to keep the heat away from the Electros and prolong their life. You can get away without it, but using it is a safety measure. When amps fail, they usually will on stage ...

[Stevem]

I found out decades ago when I use to be a smoker that the plate is way more of a air guide then a heat shield .

If you or someone smokes make this test.with amp on for 10 minutes release smoke from your mouth 2 inches away from the back panel screen.

Just release the smoke from your mouth, let it drift out, don't blow it out, then note how much smoke goes out the screen on the top of the amp.

Next do that same test again but with the steel plate removed and note how much less smoke goes out the top screen of the amp and how much just rolls around deeper into the preamp tube side of the chassis

So it's not a heat sheild so much as a air flow guide improver .

This was done on a DR103, so 4 output tubes.

I guess these days I could use my thermal gun to pin down how much cooler the outout tubes run with or without that plate.

[hulakatt]

So, I've looked around and can't seem to fin what is used to bind the wires internally on a Hiwatt? What is it? Zip ties? just extra wire?

[sluckey]

lacing cord

[martin manning]

Maybe like this? https://en.m.wikipedia.org/wiki/Cable_lacing

[Dr Tony Balls]

before the world gave us zip ties.

[hulakatt]

Should zip ties be OK to use? Heat should't be that much of an issue inside the chassis I wouldn't think.