Revox G36 and 50Hz Issues! - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th September 2013, 06:57 PM   #1
slor is offline slor  United States
diyAudio Member
 
Join Date: Jul 2007
Default Revox G36 and 50Hz Issues!

I've gained a TON of insights via the long G36 thread elsewhere on the site.

However, this is a more general question about frequency conversion and the best way to accomplish it. Revox does provide instructions on converting the motors from 50Hz to 60Hz, but this also requires a high-speed 60Hz capstan, which I'm fairly certain I'll never find.

So it appears that the easier route is to provide frequency-shifted AC. Seems like there are two "simple" ways to do this.

1. I have seen some tabletop units marketed as "overseas electronic device testers" that provide variable AC voltage a number of frequencies. These units seem relatively rare, and expensive.

2. Some folks have suggested rectifying AC, then using an inverter that puts out 220VAC (typically) at 50Hz. A common way of doing this is using a battery charger to power a deep-cycle marine battery (or possibly a capacitor and choke?), then the inverter.

Anyone have any insights? I would truly appreciate them!
  Reply With Quote
Old 27th September 2013, 07:31 PM   #2
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
You will need a very stable 50Hz power source if you expect any sort of speed stability at all. The typical battery inverter produces either a square wave or stepped sine (a misnomer since it is really a ramped square wave / trapezoid stacked on top of another - neither are suitable for powering motors. Frequency stability may not be good as well.)

Some of the older PS Audio Power Stations might be suitable as I believe they can be programmed for 50Hz output. (Investigate before buying)

You might be better off finding a 60Hz parts unit and pulling the capstan motor.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 27th September 2013, 08:10 PM   #3
slor is offline slor  United States
diyAudio Member
 
Join Date: Jul 2007
Hm. But that would leave me with a low-speed capstan, which I can't use. I'm thinking a better inverter would put out a better sine wave? (Most of them seem to be labeled "Pure Sine Wave"!)
  Reply With Quote
Old 27th September 2013, 08:23 PM   #4
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
You probably don't want an inverter, you want a synthesized 50Hz source like you talked about or something along the lines of the PS Audio power station.

At minimum something with a crystal controlled source and a perfect sine output.

Don't fall into the trap of getting something too small, remember the motor starting currents will for the reel motors will be high. A 1kVa source may not be too large.

I think you would like to minimize speed variations and be able to play things back at the exact same speed as you recorded at.

The other option might be to machine the capstan to the correct diameter for 60Hz operation.

Having the high speed capstan is desirable, but complicates things.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 27th September 2013, 08:34 PM   #5
diyAudio Member
 
Frank Berry's Avatar
 
Join Date: Sep 2003
Location: Midland, Michigan
If your machine is set up for 50Hz, isn't it also designed to operate at 220/240 volts?
__________________
Frank
  Reply With Quote
Old 27th September 2013, 08:42 PM   #6
slor is offline slor  United States
diyAudio Member
 
Join Date: Jul 2007
Yes, but the deck will accept anything from 110VAC to 240VAC, so I'm not too concerned about that.

Kevin: Many thanks, sounds like the PS Audio P300 will work well for this application. Of course, I'd like to do it cheaper, but that may not be a real option here....
  Reply With Quote
Old 27th September 2013, 09:09 PM   #7
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Check the peak rating of the P300 - you want to make sure it will not have problems starting motors. I think it will probably be fine.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 30th September 2013, 01:07 AM   #8
diyAudio Member
 
Join Date: Jan 2007
Location: Oneonta, NY; USA
Hold on a minute guys;

Slor, I gather from your posts that your machine is SLOW speed (3-3/4 - 7-1/2) and you'd like to make it HIGH Speed (7-1/2 - 15ips). I believe that the motor is 220V hysteresis synchronous, which means that it locks on to the frequency of the source. If you can't get (or have made) a larger capstan of twice the circumference, you would have to run the motor at twice it's "normal" speed (which it may not be designed for) in addition to the possible frequency conversion - so you are looking at a sine wave inverter that puts out a very stable 100 or 120hz. And the C70 phase shift capacitor (being frequency dependent) would have to be recalculated.

The "stock" motor is powered from the 220V section of a 120/220 winding on the main power transformer. You indicate that you can apparently switch taps on the input of the transformer, so you could match the output of the inverter to one of those taps, and the transformer should work correctly even at twice the frequency.

Wait a minute, maybe not - the supply and takeup motors are powered from the 120V portion of the winding - not sure if they are induction or synchronous (if you double the frequency maybe they would try to spin twice as fast - !!!???) OK, you could fix that by unwiring the capstan motor from the power transformer and running it on a separate 220V feed from the inverter. Run the power transformer from the closest voltage tap to your mains voltage. To maximize torque, the C71,72,74,75 caps on the supply/takeup motors have to be sized for the mains frequency.

My head is spinning. Sorry, but if you can't get the "correct" capstan, I'd consider giving up the project.

Charles

Last edited by stellavox; 30th September 2013 at 01:18 AM.
  Reply With Quote
Old 30th September 2013, 05:35 AM   #9
slor is offline slor  United States
diyAudio Member
 
Join Date: Jul 2007
Thanks Charles! yes originally I had a pair of low-speed 60Hz decks, but now have a high-speed 50Hz deck. I'm hunting down a 50Hz power supply, that should solve this little dilemma....

Many thanks,
Seth
  Reply With Quote
Old 3rd October 2013, 01:54 PM   #10
diyAudio Member
 
Join Date: Jan 2007
Location: Oneonta, NY; USA
Default G36 info

BTW if anyone would like copies of my Glass Audio G36 mods contact me at stellavox@excite.com.

Charles
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Revox G36 help needed! alejon Analogue Source 9 20th April 2012 10:44 AM
Please see this video and tell me what you think is the issue with this Revox G36 Salli Analogue Source 1 22nd April 2011 06:39 AM
Revox G36 Mod for preamp Jefra Tubes / Valves 3 6th February 2011 01:16 PM
revox g36 heads cone head Analogue Source 1 26th August 2010 02:52 AM
Revox G36 faults matt20102 Analogue Source 4 7th August 2008 04:51 PM


New To Site? Need Help?

All times are GMT. The time now is 09:34 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2