[David Light]

This is my first attempt at rebuilding a vintage tube amp.
I'm looking for any advice I can find on where to go and where to not
go for parts. I have a quote from Vacuum Tube Valley for a parts
package that seems reasonable. Are they reliable?

[Peter Wieck]

On Nov 1, 9:12*pm, (David Light) wrote:
* * * * This is my first attempt at rebuilding a vintage tube amp..
I'm looking for any advice I can find on where to go and where to not
go for parts. *I have a quote from Vacuum Tube Valley for a parts
package that seems reasonable. *Are they reliable? * *

Mpffffff..........

Caps is caps - type/capacitance/voltage taken into account.
Diodes is diodes - type/amperage/PIV/voltage taken into account.
Resistors have come a VERY long way in the last 40 years. Keep this in
mind.

www.mouser.com
www.newark.com

And several others will sell you good stuff at far less than boutique
prices.

Cutting to the chase.

It isn't rocket science. Replace all the original small-value caps
with good-quality equal-capacitance, equal-or-greater voltage caps. If
a ceramic cap came out, put a ceramic back in. If a paper cap came
out, put a quality film cap back in. For all electrolytics 2uF or
greater, replace with quality electrolytics as above (capacitance and
voltage). Those of 2uF or less, replace with a film cap of equal-or-
greater voltage.

Test all caps prior to installation. If you have an ESR meter, use it.
Otherwise, test at working voltage if you can.

Take your time, mind polarity on electrolytics. And diodes.

Leave no selenium diodes in place. Replace 100% of them with an equal-
or-better silicon diode. You *may* have to add resistance in some
diode circuits to replace the natural voltage drop of a selenium
diode. But NOT ALL such circuits.

Test all existing resistors. They drift. This is a PITA as you cannot
test them in-circuit. In general, I would replace the entire lot were
it my amp. Exceptions might include precision-cut resistors in the
bias circuit if they are still intact and on-spec.

Phenolic circuit boards are a PITA as the traces often break and the
connections at the tube-sockets often fail. Pay acute attention to
these. Check *ALL* connections.

I will often replace somewhere between 40% and 100% of the point-to-
point wiring if I find any fatigued joints, corrosion or other
indications of potential failure.

Take your time. Repeat: It isn't rocket science. Patience. One thing
at a time.

Take pictures of the BEFORE state of the amp. If you miss something,
it will help you find an error. USE A SCHEMATIC. Understand what you
are doing (and why) before you start to do it. ONE THING (one step) AT
A TIME.

Check your work. Test *EVERY* connection, whether you did it or not.

AND, check B+ when you are done. If you need an explanation of what
that is and means you are not quite ready for a rebuild just yet - but
all the additional information you need is a matter of a few minutes
of explanation with the schematic in-hand.*THEN* you will be ready -
mechanical skills being assumed as adequate.

Hope this helps.

Peter Wieck
Melrose Park, PA

[BretLudwig]

A good scratchbuilt project or two is much better as a start. I recommend
a regen short wave receiver first and a small bench supply and a small
amp/signal tracer second. Of course, only after you can work the problems
on the CET Associate level test on paper and have and can use the proper
test equipment.

--
Message posted using http://www.talkaboutaudio.com/group/rec.audio.tubes/
More information at http://www.talkaboutaudio.com/faq.html

[tubegarden]

Hi RATs!

Also SEE:

www.tubesandmore.com

www.digikey.com

People do not put together kits to save you money ... just effort.

Happy Ears!
Al

[tubegarden]

http://tech.groups.yahoo.com/group/eico

Duh! 4got the obvious ...

Al

[David Light]

On Sun, 02 Nov 2008 12:26:56 -0600, flipper wrote:

Thanks everyone for your comments and suggestions.

I have done business with Digikey, Newark/MCM, Parts
Express, and Mouser in the past. I have done a lot of repair and
building of solid state audio gear, and some repair of tube gear, but
never a complete rebuild like I have planned for the HF-87. I was
hoping to find a single source for the majority of the parts. Any
savings by going with 4 or 5 sources would quickly get lost in the
added shipping costs. One of the multi-section caps I just have not
been able to find at all. Since it's a power supply cap I could
probably go with a higher uF and be OK or just use 2 caps instead. I
have just joined the Yahoo Eico group, thanks to the suggestions from
here. Between this group and the yahoo group maybe I'll get through
this without that much destruction.

[[email protected]]

You can get a small PCB that you can mount regular small PCB mount
caps on which will fit underchassis on most amps.

For new builds I prefer German threaded-end lytics, the ones that
look like aluminum Euro shotgun shells. In fact they probably use the
same tooling, as radial lead US caps did with the paper bodies. It's
no coincidence many lytics have the same diameter as 20 or 28 gauge
shotshells in the US. The cap makers bought them from ammo plants.

As for oil caps, you can't get enough energy storage from any
feasible physical size for power amps. I've used GE Dielektrol motor
run caps for bench and receiver (as in radio) supplies. The "sonic
benefits" are in the imaginations of audiophools.

[Peter Wieck]

On Nov 2, 8:47*pm, (David Light) wrote:
*Since it's a power supply cap I could
probably go with a higher uF and be OK or just use 2 caps instead. *I
have just joined the Yahoo Eico group, thanks to the suggestions
from here. *Between this group and the yahoo group maybe I'll get
through this without that much destruction.

Or, considering the 'destruction' part, you could re-stuff the
problematic cap with new individual caps. They are so small these days
that it is a relatively easy task. That is, if OEM appearance matters.

Peter Wieck
Melrose Park, PA

[David Light]

On Mon, 3 Nov 2008 03:40:52 -0800 (PST), Peter Wieck
wrote:

Or, considering the 'destruction' part, you could re-stuff the
problematic cap with new individual caps. They are so small these days
that it is a relatively easy task. That is, if OEM appearance matters.

I had thought of trying that and wondered if any of the rebuilds I
had seen pictures of that looked like they had stock caps on top
actual were just shells. I'm really not that interested in making a
museum piece restoration. I'm having the chassis sand blasted and
will probably paint it some brighter color.

[David Light]

On Mon, 03 Nov 2008 11:21:52 -0600, flipper wrote:

If you want to keep the same 'look', I.E. the same can, gut the
multi-section electrolytic and re stuff it with modern caps of the
appropriate value and rating.

As I'm looking at parts that idea is looking better and better.

[David Light]

On Sun, 2 Nov 2008 18:01:44 -0800 (PST), wrote:

You can get a small PCB that you can mount regular small PCB mount
caps on which will fit underchassis on most amps.

For new builds I prefer German threaded-end lytics, the ones that
look like aluminum Euro shotgun shells. In fact they probably use the
same tooling, as radial lead US caps did with the paper bodies. It's
no coincidence many lytics have the same diameter as 20 or 28 gauge
shotshells in the US. The cap makers bought them from ammo plants.

As for oil caps, you can't get enough energy storage from any
feasible physical size for power amps. I've used GE Dielektrol motor
run caps for bench and receiver (as in radio) supplies. The "sonic
benefits" are in the imaginations of audiophools.

I may still order from VTV, but am not going with the "premium" oil
caps for sure.

[Jon Yaeger]

in article , David Light at
wrote on 11/3/08 7:22 PM:

On Sun, 2 Nov 2008 18:01:44 -0800 (PST), wrote:

You can get a small PCB that you can mount regular small PCB mount
caps on which will fit underchassis on most amps.

For new builds I prefer German threaded-end lytics, the ones that
look like aluminum Euro shotgun shells. In fact they probably use the
same tooling, as radial lead US caps did with the paper bodies. It's
no coincidence many lytics have the same diameter as 20 or 28 gauge
shotshells in the US. The cap makers bought them from ammo plants.

As for oil caps, you can't get enough energy storage from any
feasible physical size for power amps. I've used GE Dielektrol motor
run caps for bench and receiver (as in radio) supplies. The "sonic
benefits" are in the imaginations of audiophools.

I may still order from VTV, but am not going with the "premium" oil
caps for sure.


In the opinion of some, the HF-87 is probably the best sounding power amp
kit ever offered.

I'm rebuilding two of them . . . one on my own chassis, and another with a
chrome-plated original. Heyboer offered a modern, upgraded version of the
power tranny. They may still be available.

In the meantime, check out the Eico user group on Yahoo.

Good luck!!

Jon

[[email protected]]

On Nov 4, 3:56*pm, Jon Yaeger wrote:
in article , David Light at
wrote on 11/3/08 7:22 PM:



On Sun, 2 Nov 2008 18:01:44 -0800 (PST), wrote:

You can get a small PCB that you can mount regular small PCB mount
caps on which will fit underchassis on most amps.

For new builds I prefer German threaded-end lytics, the ones that
look like aluminum Euro shotgun shells. In fact they probably use the
same tooling, as radial lead US caps did with the paper bodies. It's
no coincidence many lytics have the same diameter as 20 or 28 gauge
shotshells in the US. The cap makers bought them from ammo plants.

As for oil caps, you can't get enough energy storage from any
feasible physical size for power amps. I've used GE Dielektrol motor
run caps for bench and receiver (as in radio) supplies. *The "sonic
benefits" are in the imaginations of audiophools.

* I may still order from VTV, but am not going with the "premium" oil
caps for sure. *

In the opinion of some, the HF-87 is probably the best sounding power amp
kit ever offered.

I'm rebuilding two of them . . . one on my own chassis, and another with a
chrome-plated original. *Heyboer offered a modern, upgraded version of the
power tranny. *They may still be available.

In the meantime, check out the Eico user group on Yahoo.

Good luck!!

Jon

It's always best to use a guitar amp power transformer where there is
one that will work nicely because the supply of future replacements is
assured. Unless rock and roll guitar utterly vanishes in popularity.

You can also use a common 115: 240/480 HVAC control power transformer
and a separate heater transformer. These transformers are for locally
operating 115V devices in air conditioning systems where the unit is
supplied by 480vct or 240vct high power lines. They all have a matched
double primary for series or parallel operation which you use a sthe
secondary. They are all rated for heavy duty service with potting and
a tough coating.


This is Jeff Medwin's shtick. Mind you I agree that he's deranged
about his theories of power supply design, but these do work well.

[David Light]

On Tue, 04 Nov 2008 16:56:04 -0500, Jon Yaeger
wrote:

In the opinion of some, the HF-87 is probably the best sounding power amp
kit ever offered.

That's good to know. I friend of mine gave the amp to me about 15
years ago. Recently I have been building some mic preamps for the
studio, and the HF-87 called to me from across the room. The chassis
should be getting sand blasted tonight.

I'm rebuilding two of them . . . one on my own chassis, and another with a
chrome-plated original. Heyboer offered a modern, upgraded version of the
power tranny. They may still be available.

Are you gonna have some pictures on a web site somewhere?

Hopefully I won't need any transformers. They all did work 15 years
ago when I last had the amp on. It did make sound and a lot of hum
also which I assumed were the old power supply caps. More recently
the transformers tested OK ohm wise.

In the meantime, check out the Eico user group on Yahoo.

I have joined the Yahoo group as suggested here (thanks) and have
learned a bit more about the amp.

[David Light]

On Sun, 2 Nov 2008 08:57:35 -0800 (PST), tubegarden
wrote:

People do not put together kits to save you money ... just effort.

A friend of mine gave me a good portion of the caps that I need. So
the kit plan is off. So now I'm up to $14 invested in the amp +
rebuild. The $14 was for spray paint.

I was thinking about changing all the tube sockets with the porcelain
type. After taking a good look at the old sockets they seem more
rugged than the ones in my fairly new guitar amps and still in good
shape.