Newly acquired Presto 6n, 1d, 92a! Help me join the club?

[ihoover]

Hey all,

Indiana here. After ages of lurking, and months and months of inquiry / searching to find a cutting system of my own, I've finally gotten my hands on a Presto 6n lathe, a 1d cutter head, and a 92a amp. I'm stupidly excited... and also pretty nervous. Perhaps you remember the feeling.

All things considered, most of this gear looks to be in pretty decent shape, despite the fact that none of it has been used or powered on since 1970.

I'm planning to get this system up and running in order to make direct to disc old-time music recordings (at both 78 and 33 rpm). I've done some homework / forum reading, and have general grasp on what I need to do next... but I also have quite a few questions. My apologies in advance for the dumb ones. I'll try my best to avoid them, but I know they're out there. Here are some questions to start, with photos and more questions below:

1. Right off the bat, I'm missing the dashpot and the 78 rpm rubber puck / idler wheel. Does anybody have a spare of either? Please pm me. I've seen the DIY guides for dashpot construction if nobody has one.

2. The motor is untested and needs a cleaning. I've opened it up twice but really have no idea what I'm doing. The wire sleeving on the motor is also pretty frayed and grimy. Should I find a small motors repair shop and have them take a look?

3. I've tested the continuity of the cutterhead with an multimeter / ohm meter. It fluctuates between 2.4 and 2.8, usually settling closer to 2.4. If i reverse the red and black test leads, it tests closer to 3.5. The back of the cutter head reads 500 ohms.

Presto 6n, with new housing.


Overhead unit / assembly. Missing dashpot.


Chassis topside, with missing 78 rubber puck / idler wheel.


Bodine motor, unattached for cleaning.


Bodine motore detail. Frayed wire sleeving.


Chassis bottomside, with motor unattached for cleaning.


Chassis bottomside, electrical wiring questions! Help!
When is comes to electrical wiring, I'm kind of in the dark. I've done some soldering for patch bays and 1/4 inch cables... but not much else. I don't know what gauge of wires to use for each connection, and I also don't really know what anything is. Hence the diagram below. Can anybody help me identify 1-10? I've included my best guesses using the 6n Manual.

1. ?
2. Switch capacitor? What does it do?
3. Motor starting capacitor
4. I think one of these is the Cutter C-R network?
5. I think one of these is the Cutter C-R network?
6. 3 pin jacks, for connecting amp to cutterhead. What kind of wiring do I use to replace this****?
7. Red and black pin jacks = 78?
8. white and black = 33?
9. Spare Tonearm wiring?
10. Spare Tonearm wiring?



92a amp, with new housing.


92a amp, inside wiring.


92 amp backside. The amp is probably the biggest mystery for me. I've yet to turn it on. One of the tubes is missing a center pin, the rest seem fine. I'm readying to just send the amp to a repair tech. Any thoughts? Should I pre-buy tube replacements or just let them do it / figure it out? Also, I need to figure out how to get signal from a mic/mixer to the amp and then to the 6n. All of that wiring is gone. Does anyone know?


92amp backside detail. Wiring questions.


Tube (5R4GY's) with missing brown plastic center-pin.


Tube detail.


1d cutter head, rated for 500 ohms.


1d cutter head, inside look.


1d cutter head resistance testing, fluctuating between 2.4 and 2.8.


Tonearm for future use. I don't have a cartridge for this right now, and isn't essential just yet.

[Prestofan]

You have gotten some great equipment. first, do not turn on the amplifier. If it has not been used for 30-40 years, turn it on slowly using a variac and adjust to 110 volts slowly over a couple of hours. Replace the tube with the broken center pin or be sure land align it properly. I would suggest taking the motor to a shop. I always did when getting a used 6N.

If the coils in the head appear OK it might, because of age need to be re-magnetized. When recording, if the volume seems to low, it might.

Beware of some of the attachment screws next to the power cord connections. This amp, as well as most high power amps has an output for connecting external equipment and will be at 450 volts. Do not touch when amp on!

You might likely be able to get a replacement rubber puck from Terry's Rubber Rollers. Also if too hard or any flat spots, he does an excellent job of re-vulcanizing.

If you need a manual on the 92A amp, pm me. I have copies available. You could operate OK without the vertical damper.
I have seen lots of 6N without them.

Could luck. You will receive lots of good help here. Your equipment looks clean and I think you have a micro groove lead screw.

Alan Graves

[ihoover]

Wow! Thanks for writing Alan. You're a legend on here!

I'll look into the Variac and thank you for the forewarning about the 450 volt attachment screws on the amp. I'd likely have fried myself otherwise.

I've heard about Terry's Rubber Rollers, I'll reach out. I also have an PDF of the 92a manual (thanks to this forum), but thank you for the offer.

And yes, the lead screw is 120 LPI (IO).

Thanks again Alan. I hope to be in touch again sometime!

Cheers,
Indy

[tragwag]

connections to the amp are those terminal lugs that appear to be below the back transformers.
read in the manual it mentions which lugs are for which output impedance, you'll want the combo thats at 500 ohm

[markrob]

Hi,

That resistance reading is weird. Based on the meter setting, I'm reading 2.5K ohms. That's very high. The pin jacks use a screw clamp to make contact with the wires. Try tightening them or better yet, measure at the head or at the ends of the wires. If its a 500 ohm head, I'd expect resistances in 180 ohm range. I didn't notice if you took a photo of the rear of the head. The factory wound impedance is stamped there. Take that with a grain of salt as the head could have been re-wound at some point.

Mark