Magnavox Updated 86-01

[Mike Stehr]

Probably not in a build like this, tie all your grounds together at a central
location then connect those to the chassis an you should be just fine.

If at all possible I do try an keep the power supply grounds to there area
and the signal ground to another area further away from each other though.

With regard to the output transformer secondary common taps-My retired EE friend mentioned to chassis ground the secondary common leads, and then have the negative speaker common binding posts chassis grounded at another location. Not at the same location.

Or don't use the secondary common leads right to the speaker common binding posts, and then grounding them to the chassis.

IIRC, he mentioned something about eddy currents...not really too sure as why, I just followed directions.

 

[cephelps]

OK and Thanks for that information.

 

[cephelps]

Photos of cleaning of the chassis, painting of chassis, installing of some of the components. Waiting on just a few more parts, then get it wired.

 

[Joe Willis]

Looks good, what kind of paint is that?

 

[Thespeakerdude8]

Very nice job! I like the hammertone! I've GOT to get pics of my latest 8802's up here! I did them in Hammertone gray with oak skirts stained gunstock with a radio shack chrome volume knob. I left the PT's alone because they were nice, but I polished up the OT frames and clearcoated them.

Interesting about the output transformer hookup, I'll have to look into that. I originally built my 8601 (my avatar) as an RH84, but I due to cramped quarters I can't really get rid of power supply ripple 'cause I can't fit a choke or large filter cap in there. I could remove the can and go solid state on the rectifier but that would take the fun out of everything!

Let us know how this modified 8601 circuit works out for you, I might just have to convert mine back and see how it sounds.

 

[cephelps]

The paint is Rust-oleum Hammered on the top, and R-O primer on the under side. It will be crimped, but I think I will make it. I will start wiring, and I will post my progress.

 

[kpaxfaq]

Looking good! I've been lurking looking for a good first time build circuit and this looks relatively straightforward! :thmbsp:

Keep us updated!

 

[cephelps]

Sure will.

 

[cephelps]

This has been a slow build, due to waiting for parts and running out of room to install components. Here are a few problems I am having and not to sure of. I had to parallel a 50uf and a 10uf electrolytic to get the 60uf I needed. I had to relocate the 150uf electrolytic from the underside to the top side. Now, is the 3/8" space between the 150uf cap and the 6EU7 tube to close? I have taken all of the recommendations from this updated circuit, but I am running out of room. I have not installed the 0.22uf coupling caps yet. I have ordered two sets of MP sizes. One thing I find myself doing is trying to use high end components, higher wattage, higher voltage components, and some added features. May be I should have just used a bigger chassis.

 

[clydeselsor]

Nice work!

 

[ferninando]

ditto

 

[cephelps]

With regard to the output transformer secondary common taps-My retired EE friend mentioned to chassis ground the secondary common leads, and then have the negative speaker common binding posts chassis grounded at another location. Not at the same location.

Or don't use the secondary common leads right to the speaker common binding posts, and then grounding them to the chassis.

IIRC, he mentioned something about eddy currents...not really too sure as why, I just followed directions.

I have taken your advice to connect the speaker Grounds to the chassis ground. Everything else is connected to a common ground witch is connected to the chassis ground at another point from the speaker ground. The two big green wires are the speaker grounds. I need to read more about eddy current. I remember the name, but that is all.

 

[Kegger]

Yes that is defiantly a small and cramped chassis, just enough room to build the amp.
(you did well making it all fit, that volume control certainly takes up some room)

I would not set-out to build an amp like that in small quarters as it is, but for a rebuild
I used it and had enough room to get the job done, having said that this amp isn't the
type of amp I'd be to worried about building some great chassis for, it's a decent little
amp that performs fairly well within the parts available.

I'd save my time and resources for the next bigger/badder/better build an do it with a
few better parts, output trannies, power tranny, choke in the supply an bigger chassis.

For that build those parts and chassis are about equal, I'd build with what is there.
(It's a pretty nice little amp)

 

[Mike Stehr]

You just gotta keep it simple...

 

[Kegger]

Wow Mike, that is some killer clean work/layout there..:thmbsp:

 

[cephelps]

Simple, I would have like too if I had just rebuilt the Maggie. I built the Magnavox Updated 86-01, which has more components, plus the ones I added. It was a challenge, and could be a great improvement over the Maggie 86-01. The designer thinks it is a great design, and I wanted to try this amp. A few more parts and a wood frame, I will soon see. I will keep you posted. That is a great looking amp you got there.

 

[Kegger]

That little maggie is not a bad little amp at all, the design/redesign was basically
a cleaning up of the signal and making things run a bit better then stock really.
(your rebuild looks quite nice, there are better circuits then the maggie here)

--------

Since your running single cathode resistors on the outputs you did remember the
value change doubles from what the shared resistor values that were in there. :scratch2:

 

[cephelps]

Yes that is defiantly a small and cramped chassis, just enough room to build the amp.
(you did well making it all fit, that volume control certainly takes up some room)

I would not set-out to build an amp like that in small quarters as it is, but for a rebuild
I used it and had enough room to get the job done, having said that this amp isn't the
type of amp I'd be to worried about building some great chassis for, it's a decent little
amp that performs fairly well within the parts available.

I'd save my time and resources for the next bigger/badder/better build an do it with a
few better parts, output trannies, power tranny, choke in the supply an bigger chassis.

For that build those parts and chassis are about equal, I'd build with what is there.
(It's a pretty nice little amp)

I feel some what the same as you do, but I have time and resources to play around with these amps. I am looking forward to the next SE amp project. If you come up with another design, I would like to consider it along with the others I am looking at.

 

[Mike Stehr]

Simple, I would have like too if I had just rebuilt the Maggie. I built the Magnavox Updated 86-01, which has more components, plus the ones I added. It was a challenge, and could be a great improvement over the Maggie 86-01. The designer thinks it is a great design, and I wanted to try this amp. A few more parts and a wood frame, I will soon see. I will keep you posted. That is a great looking amp you got there.

Your amp looks great. That amplifier is my second 86XX series type, and the first amp doesn't look that nice.
Circuit-wise, it's just a bare bones 6EU7 cap/resistor coupled amp, with shared cathodes for finals. The stock Magnavox feedback resistor values are used, with frequency compensation capacitors bypassed across them. (using a scope)
Nothing wrong separating the cathodes of the output tubes, you are probably better off...

I think a part of the Magnavox "sound" is some of the SE and PP console amplifiers share the cathodes of the output tubes. A hall-effect type of sound is aquired...who knows...

I would think Paul's version of SEP maggotbox sounds great.

RH84 is a good single-ended 6BQ5/EL-84 circuit. I'm doing a scratch build amplifier around it.

Mike

 

[cephelps]

That little maggie is not a bad little amp at all, the design/redesign was basically
a cleaning up of the signal and making things run a bit better then stock really.
(your rebuild looks quite nice, there are better circuits then the maggie here)

--------

Since your running single cathode resistors on the outputs you did remember the
value change doubles from what the shared resistor values that were in there. :scratch2:

Yes, I got the information on what to do form you. Drop the 10 ohms and change the RC to 250 ohms and 300uf cap. I was not able to find a 250 ohms so I use a 240 ohm. Is that a workable set up?