• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Another Maggy Thread

Sorry I don't have a schematic and can't show the underside as it is very hard to disconnect from the box (with speakers) I have it mounted in, but here is my 175-67 modded with ultra-linear output transformers. The power filter cap is still original and I replaced the grid caps (.047 @600V) with .01 @600V orange drops. Replaced just a few out of spec resistors and left the hum balance pot in place. The original 6V6 tubes were replaced with 6L6GC tubes.

maggie3.jpg


You can barely see the square magnets (left & right of the amp) but they are also the original magnavox 15" woofers.
 
Thespeakerdude8 said:
can that PT really dish out enough juice for a quad of 'L6's???? :yikes:
Click to expand...

Plenty of power sinse I'm not using the tuner/pre-amp that originally powered off of the amp. It's clean, loud, and plenty of eyeball rattling bass. I have the original tuner/pre-amp that I modded with a 6CA4 rectifier and seperate power transformer so I can use with any amp set-up.
 
Power consumption

Excellent question on the power usage of the 6L6

I do know that a lot of those consoles would have had at least two more tubes for the remote preamp section.

The power transformer is so big on mine. it is 4.5" tall and a full 1.5" taller than my other maggie PT. weighs a full 12 lbs.

And I really really love the way coke bottle 6L6 tubes look!

Only reason I am fooling with 6V6 is I did not have any guitar amps that used that tube and people dearly love their fenders based on it. Old tweed single ended amps, deluxe reverbs . . . /knife's eyes glaze over as he wanders off the subject . . .

I would love info on your preamp schematic cademan
 

Attachments

  • magnavox power transformers - big diff huh (small).jpg
    magnavox power transformers - big diff huh (small).jpg
    69.9 KB · Views: 187
  • magnavox chassis with transformers mounted small.jpg
    magnavox chassis with transformers mounted small.jpg
    103 KB · Views: 214
  • magnavox chassis with caveman cutout for 2nd OPT small.jpg
    magnavox chassis with caveman cutout for 2nd OPT small.jpg
    90.2 KB · Views: 175
  • magnavox chassis sideshot to check trannie alignement small.jpg
    magnavox chassis sideshot to check trannie alignement small.jpg
    24.2 KB · Views: 154
knifefighter said:
Ok, I downloaded Tiny Cad, and I was able to knock out an original to replace the one I posted earlier. (see above post)

And I tried to implement the changes recommended.

Any more changes let me know, this is the audiophile maggie 175 build. . . . LoL

Ok, well, it is as audiophile as it gets at knife's cave.

Feel free to pick it apart, or add!
Click to expand...


That's it, especially the amazing speaker part.:D I test run all mine on Klipsch Heresys (modded) and it's a match made in heaven.:music:
 
if any of you guys are worried about 6L6's taxing the power supply, you can always do what I've done with my little 88- series magnavox . . .

I use Coke Bottle 6V6G's :thmbsp:

same ratings as 6V6GT, jjust cooler 'cause they got that lovely hourglass figure . . .

btw, I've recently snagged another 185 - chassis console, so I will start a thread VERY soon documenting the conversion of this to the 175 - circuit . . .

I have one of these conversions under my belt, thanks to Gordon's tips, and if you take your time, it's a pretty easy job . . .
 
amp175xx or 185xx

What is difference between the 2, My guess is when the tuner preamp came as a option you got the amp175 if not the amp185 incorporated the circuit for boosting the signal for the turntable. my statment is that I parted a console that has turntable only and used the 185,with bass treble and volume controls but there was not a preamp which I am used to. I just found a 175 console recently but it has a tuner preamp with it but omits the 7025 tube circuit that the 185 has. otherwise look identical.Any thoughts on this.Anyway I like the amp128,142s better these are the mono type with the 4 6v6gt, 2 5y3 rectifier. These seem heavier duty than the 175 type.Am I wrong? any input would greatly be appreciated.
 
33uf cap with dual 5Y3GT?

So,

I discovered that 33uf@450v caps are much much cheaper than the 30uf called for in the power section as the first capacitor after the dual 5Y3GT. (about $5 vs $13) And so I bought those.

But, the 5y3gt shows 20uf as max, they chose 30 in the design.

Think I should seriously check myself and cobble some other caps together to stay under 30uf at all costs?

Dan
 
Hi Jeff

Hi Jeff,

Ya, the output iron on those mono amps is heavy duty compared to the 175. I am not sure how different the impedance is. (mine are 5400 - 5600 with 8 and 16 taps)

I am hoping that means better sound when I am done!

So, what I have left over right now is the 142AA chassis minus the OPT, and no control parts came with it. I guess I am different than most, I just started replacing caps without even testing anything . . . but then I threw out my box of parts by mistake and so it sat in the shop for years. I was just so disgusted at throwing out $100 in parts for repairs and then tweaking values, pin straighteners, who knows what all. That was 10 years ago I bet. So I decided to get over it and here I am :) And the parts cost more now!!!

I think I have pics of the 185 and 175 system, want me to post them Jeff?
 
jeffhamman said:
What is difference between the 2, My guess is when the tuner preamp came as a option you got the amp175 if not the amp185 incorporated the circuit for boosting the signal for the turntable. my statment is that I parted a console that has turntable only and used the 185,with bass treble and volume controls but there was not a preamp which I am used to. I just found a 175 console recently but it has a tuner preamp with it but omits the 7025 tube circuit that the 185 has. otherwise look identical.Any thoughts on this.Anyway I like the amp128,142s better these are the mono type with the 4 6v6gt, 2 5y3 rectifier. These seem heavier duty than the 175 type.Am I wrong? any input would greatly be appreciated.
Click to expand...

The transformers on the 175 & 185 might look the same size physically, but the 6.3 volt heater tap on the 175 has more current capabilities because it is driving the heaters of 7 more tubes included in the tuner/pre-amp. Don't have the specs onhand, but I do remember doing a little calculating when I removed the tuner/pre-amp from the equation and used the 6L6GC's on the 175 amp.
 
knifefighter said:
So,

I discovered that 33uf@450v caps are much much cheaper than the 30uf called for in the power section as the first capacitor after the dual 5Y3GT. (about $5 vs $13) And so I bought those.

But, the 5y3gt shows 20uf as max, they chose 30 in the design.

Think I should seriously check myself and cobble some other caps together to stay under 30uf at all costs?

Dan
Click to expand...

with two 5y3's in parallel, I'm pretty sure it doubles the acceptable value of that first cap. . . so it *could* handle 40 uf :scratch2:

at least I think thats how it works . . .
 
markus said:
with two 5y3's in parallel, I'm pretty sure it doubles the acceptable value of that first cap. . . so it *could* handle 40 uf :scratch2:

at least I think thats how it works . . .
Click to expand...

It would sure seem that way to me, but I've been told both ways (yes and no).:dunno: I personally wouldn't worry about running a 33 on one, but that's me (especially with NOS tubes). Again, just me, but I've pushed those ratings to double and have never had a rectifier failure in any amp ever. Magnavox (and others) pushed them too. I don't know if it's because tubes warm up slow or what, but I've done a lot of testing with power supplies, and never see any spikes or overload conditions using an inline ammeter. All that being said, I'm from the Pakprotector school of power supplies, so if I had a chance to use two rectifiers instead of one, I certainly would.:yes: I would also bypass all the lytics with at least a film cap of .22uf, and preferably a second one of .022. I use Nichicon polyesters for that.
 
Great thread!! I have a pair of amp-150's and have been wondering If I could convert them over to ppp 6L6 If not pp is great as well.
These amps are ppp 6v6 and also have a se 6v6 section, if the 175 pt's can run a quad of 6L6 I dont think these would have a prob.
After removing both the old output transformers I should have enough room to slap on some serious iron.
 
jaymanaa said:
It would sure seem that way to me, but I've been told both ways (yes and no).:dunno: I personally wouldn't worry about running a 33 on one, but that's me (especially with NOS tubes). Again, just me, but I've pushed those ratings to double and have never had a rectifier failure in any amp ever. Magnavox (and others) pushed them too. I don't know if it's because tubes warm up slow or what, but I've done a lot of testing with power supplies, and never see any spikes or overload conditions using an inline ammeter. All that being said, I'm from the Pakprotector school of power supplies, so if I had a chance to use two rectifiers instead of one, I certainly would.:yes: I would also bypass all the lytics with at least a film cap of .22uf, and preferably a second one of .022. I use Nichicon polyesters for that.
Click to expand...

in the 150's I upped the 1st input filter cap to 100uf I know I'm over the 80uf rated for 2 5u4's in parallel but have never had a prob yet they are photoflash caps. Then after the choke I have a 440uf photo flash can, I know I am at the bleeding edge of the voltage limits of these caps but no problems so far!
 
Good info

Thanks for the update.

I am using Old - Old stock - OOS tubes

I think I have a stash of tested and labeled tubes someplace to match up.

I am glad to hear real world experiences on first capacitors after the rectifier tube.

Ok, back to my wiring.

Dan
 
Just FYI on the rectifiers for those messing with these Maggie amps. (or others)

The 5Y3 and 5U4 are both directly heated NON slow warmup rectifiers.
They both have a fairly large voltage drop, meaning the voltage will sag more.

The 5Y3 is a 2a heater, 125ma max
The 5U4 is a 3a heater, 225-275ma max (depending which version)

There are 2 other rectifiers I would use in there place, (drop in, same pinout)

The 5AR4 is a 2a heater, 225ma max
The 5V4 is a 2a heater, 175ma max

The 5V4 and 5AR4 are both indirectly heated, slow warmup rectifiers.
They both have a farly low voltage drop, meaning the voltage won't sag as much.

They can both handle fairly large cap inputs, (Won't need as much without the sag)

5V4's, plentiful an rather inexpensive, plus they come in the 5V4G variety, ST shape!
 
You must log in or register to reply here.
Back
Top Bottom