What's the idea behind this?

[gyraf]

Could we have pics and measurements of the reactor?
DC resistances and perhaps inductances at no-load? Transfer ratio if set up as transformer?

We should be able to get this working

 

[thelivingroom]

Could we have pics and measurements of the reactor?
DC resistances and perhaps inductances at no-load? Transfer ratio if set up as transformer?

We should be able to get this working

DCR primary: 215 Ohms
DCR secondary: 2 Ohms

L primary: 3.63H
L secondary: 22.8mH

Wired like a transformer, with 7.5VAC on primary, it has 172mV out of secondary.

Physical size: 40.4mm W (44.9mm o/o of yellow tape) x 35.2mm D x 11.3mm H (28.1mm H including bobbin)





I’ll get it all set up again and make sure I didn’t miss something. My brain was really tired by Friday evening. I was thinking I may disconnect the feeds to the threshold and reactor to take the side chain out of the equation, and manually feed current to the reactor via a supply and potentiometer just to make sure it’s passing signal at full range. If so, then it’s probably fine and back to side chain troubleshooting I’ll go.

 

[Gold]

That’s a very intriguing design and unit, I wonder how it sounds ?!

Thanks for drawing the schematic in such a clear / readable / elegant way !

It is difficult to set up outside a cutting system. The side chain needs to be fed an RIAA encoded signal to work properly. It was intended to be part of the Ortofon 600 series cutting amplifier rack.

The termination of the audio and side chain need to be specific values for the frequency response to be correct.

It is still a bit slow or imprecise for its intended purpose of cutterhead protection. The sound quality of the circuit is excellent.

 

[thelivingroom]

Could we have pics and measurements of the reactor?
DC resistances and perhaps inductances at no-load? Transfer ratio if set up as transformer?

We should be able to get this working

Good news: the reactor is fine. I disconnected the side chain and manually fed the reactor current via a supply and potentiometer with a looping 20-second sweep from 5-20kHz playing through the unit, and once I got to about 35mA of current the response stayed flat. When I dropped it to the 15mA that I was previously getting out of the side chain, the tilt of 5kHz boost down to big 20kHz rolloff reappeared. Time to reinvestigate the side chain, and now I know I need at least 35mA going to the reactor before I can even begin to try adjusting the 20kHz and 7kHz trimmers.

 

[Gold]

Here is a beautifully restored Ortofon/Lyrec cutting system. I think I see the STL632 in the left vertical rack in the top spot.

 

[Brian Roth]

@Gold Why two preview heads?

Bri

 

[thelivingroom]

Here is a beautifully restored Ortofon/Lyrec cutting system. I think I see the STL632 in the left vertical rack in the top spot.

Wow, that is some amazing and beautiful equipment. Thanks for sharing!

 

[Gold]

@Gold Why two preview heads?

Bri

I’m not familiar with that Lyrec preview deck. Possibly spaced for 33 1/3 or 45 at 15ips. Or spaced for 15ips and 7.5ips for 331/3 rpm records.

 

[thomasdf]

Beautiful setup !
That video is 10 years old now, and I’ve checked their website and no mention from either the cutting kit or the engineer in the video

Thanks for the explanation regarding the deesser discussed here. Reminded me of the infamous Ortofon, indeed

 

[Gold]

Sean Davis is the lathe guru of the UK. He is still around but no longer making house calls. I’ve met him a few times and he was always a fountain of lathe knowledge.

Sean did the restoration. I don’t think he was doing the cutting for the label that owns it.

 

[gyraf]

Time to reinvestigate the side chain, and now I know I need at least 35mA going to the reactor before I can even begin to try adjusting the 20kHz and 7kHz trimmers.

Please note that the TL084 maximum (short circuit protection) output current is 26mA - so there's something skewed here

Could it be that the core has been permanently-magnetized by accident?

 

[thelivingroom]

Please note that the TL084 maximum (short circuit protection) output current is 26mA - so there's something skewed here

Could it be that the core has been permanently-magnetized by accident?

That’s possible, and about the only thing that makes sense, because I don’t think it’s totally dead. I don’t have a magnetometer to check it. Is it possible to try to demag it with a Han-D-Mag, or by reversing the leads of the DCR test?

After looking at the specs of the TL084 the other night I realized that more current wasn’t the solution, or possible. I also worked out the math of what the current from the +15v line to the reactor should be at idle based on the schematic, and it’s spot on. And at pin 13 of U3, where the junction of the +/-15v lines meet, I just need to trim RV2 a tiny bit to get them to null at 0v (PSU is about .3v difference between +15 and -15). I then monitored the side chain again while varying frequencies and threshold, and both current on the DMM and DC levels on the scope are coinciding with those variances, so I do believe that the side chain is functioning properly.

 

[gyraf]

yes, I'd expect your tapehead demagnetizer to be useful here (I've once defluxed a pv76 output transformer core like that).

 

[thelivingroom]

yes, I'd expect your tapehead demagnetizer to be useful here (I've once defluxed a pv76 output transformer core like that).

I had hope, but that didn’t fix it. No change at all. I did the same as on my tape machine, starting a few meters back, moving in slowly to within a few mm, then backing away slowly before unplugging. I’m about to send an email to Manley to see if by some miracle they have one of these reactors stashed somewhere. For the time being it’s going back on my junk shelf, leaving me feeling a little smarter but discouraged haha.