UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players

Notices

Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

Closed Thread
 
Thread Tools
Old 6th Mar 2017, 3:58 pm   #21
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: How to bias Philips EL 3536 valve tape amp?

For measurements where the circuit voltage is high then switch the probe to X10.

Lawrence.
ms660 is offline  
Old 6th Mar 2017, 4:12 pm   #22
ricard
Octode
 
ricard's Avatar
 
Join Date: Mar 2006
Location: Lund, Sweden
Posts: 1,631
Default Re: How to bias Philips EL 3536 valve tape amp?

Normally you would do that anyway to get the probe compensation circuit switched in. And especially in that position, it's not a problem to measure a couple of hundred volts with an oscilloscope.
ricard is offline  
Old 7th Mar 2017, 11:37 am   #23
Clockwork_TV
Pentode
 
Clockwork_TV's Avatar
 
Join Date: Aug 2007
Location: London, UK.
Posts: 115
Default Re: How to bias Philips EL 3536 valve tape amp?

Hi All

I've attached result pics from my CRO.
I attached a 1kHz signal generator to the mic input, set it to PA and recorded the o/p across one speaker channel. Top is input bottom is output, (sine then square wave).

It was quite a quiet signal going in. So mainly seems to be high freq boost? Or bass cut? I think the peak seemed to increase when I turned up the input. Now this is the mic i/p which uses an extra bit of circuitry to the tape head. Also I realised afterwards the tone control was set to full treble - not sure if this does anything on PA (the volume knob doesn't do anything on PA - it's the mic i/p that adjusts volume).

Is there a better place to apply the signal eg on the tape head somewhere to get a better idea about playback? I wonder if should I record the signal on tape and play it back and test this.

Cheers John
Attached Thumbnails
Click image for larger version

Name:	IMG_20170307_000834.jpg
Views:	65
Size:	64.7 KB
ID:	138762   Click image for larger version

Name:	IMG_20170307_000743.jpg
Views:	68
Size:	51.4 KB
ID:	138763  
Clockwork_TV is offline  
Old 7th Mar 2017, 6:54 pm   #24
Clockwork_TV
Pentode
 
Clockwork_TV's Avatar
 
Join Date: Aug 2007
Location: London, UK.
Posts: 115
Default Re: How to bias Philips EL 3536 valve tape amp?

Quote:
Originally Posted by ms660 View Post
For measurements where the circuit voltage is high then switch the probe to X10.
OK good tip will try thanks
Clockwork_TV is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 5:54 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.