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Little tech questions from your day

All your geeky questions about electronics, microphones, tape machines, etc.

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Re: Little tech questions from your day

Postby numberthirty on Tue Dec 18, 2018 7:49 pm

J. Burns wrote:Interested! hit me up at thejamesburns @ gmail


Copy that. Give me a couple of days to see what's what, and I'll send you an e-mail.
154 wrote:Are you in Voivod or something?
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Re: Little tech questions from your day

Postby japmn on Thu Dec 20, 2018 6:07 pm

scrotescape wrote:@japmn
That looks like the center tap of the b+ winding where you lifted the lockwasher ring connector. That needs to connect to ground/chassis. The green wire on 3prong cord also needs to connect to chassis. I’d cut that death cap out completely.


The picture is confusing. The cap is floating in the pic, but looks like it is attached to the fuse. The cap is not connected to anything but the lug. It's actually completely gone now. the problem I'm having is, if the center tap lug is connected to the chassis, the fuse pops. If it is not connected, the amplifier works just fine. If i measure voltage from center tap to chassis it is 300v.
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Re: Little tech questions from your day

Postby Adam P on Thu Dec 20, 2018 7:14 pm

The 300V makes sense in that case (I think) since you’d have 600V between the secondaries for the rectifier tube plates, and the center tap would be between them.

Total shot in the dark...does it blow fuses with the center tap grounded and the rectifier tube removed?
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Re: Little tech questions from your day

Postby japmn on Thu Dec 20, 2018 10:39 pm

Yes
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Re: Little tech questions from your day

Postby numberthirty on Fri Dec 21, 2018 9:21 pm

numberthirty wrote:Just spit balling this one since I haven't actually heard the issue.

Hiwatt DC40. Sent in for repairs because of a volume drop after fifteen or twenty minutes of playing time. Repair completed. When tested post-repair, the issue seems as bad. Potentially worse. Apparently(going by the description I was given), even cranking the master yields almost no volume increase.

Anyone ever ran into anything like this on a master volume amp?


An update on this front...

After the repair that seemed to iron the problem out, my brother mentioned dealing with the exact same issue.

The other day, he came by and mentioned that he had been using the second "Speaker Out" jack without issue.

After I said that bit of info probably narrows things down quite a bit, he agreed and we had a decent chuckle.
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Re: Little tech questions from your day

Postby scrotescape on Sat Dec 22, 2018 8:39 am

@japmn
Maybe ohm meter with rectifier out and ct floating:
Check for short on secondary and from pri to sec.
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Re: Little tech questions from your day

Postby hylje on Fri Dec 28, 2018 1:20 pm

Apparently the filter caps of my Traynor TS-50 are going bad. Is it a big operation to change them? I do have an electronics repair shop downstairs, so I probably won't even think about doing it myself. They are not amp repair guys, so there is that. Is there anything special one should know about changing them?
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Re: Little tech questions from your day

Postby biscuitdough on Fri Dec 28, 2018 2:51 pm

Most electronics have electrolytic caps in them, so they'll know about installing them with correct polarity and how to choose acceptable substitutes if the exact ones aren't available. You can ask them to use long-life caps instead of the basic models. It's only a few cents difference in cost.

Solid state amps often use electrolytics in places other than the power supply filters - many more than a tube amp would use. It may be a similar cost, or at least not astronomical, to have them simply replace all electrolytic caps in the amp, and clean and reflow all solder joints. They will all go bad eventually.
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Re: Little tech questions from your day

Postby hylje on Fri Dec 28, 2018 3:27 pm

Right! Thanks!
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Re: Little tech questions from your day

Postby Dr Tony Balls on Mon Jan 07, 2019 12:45 pm

File under: I am smart at some things and really dumb at other things....

I am borrowing a little M-Audio dual interface that has phantom power but only applies it globally to both channels (i.e. if its on for mic one, it's on for mic 2). If I have it on and connect a non-phantom mic (SM57) to the interface, will it fuck things up in some way? Will it work?
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Re: Little tech questions from your day

Postby Boombats on Mon Jan 07, 2019 12:48 pm

Dr Tony Balls wrote:File under: I am smart at some things and really dumb at other things....

I am borrowing a little M-Audio dual interface that has phantom power but only applies it globally to both channels (i.e. if its on for mic one, it's on for mic 2). If I have it on and connect a non-phantom mic (SM57) to the interface, will it fuck things up in some way? Will it work?

No you're fine as long as they aren't ribbon mics (some of which are ok with phantom anyway)
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Re: Little tech questions from your day

Postby ldopa_chicago on Mon Jan 07, 2019 12:50 pm

Dr Tony Balls wrote:File under: I am smart at some things and really dumb at other things....

I am borrowing a little M-Audio dual interface that has phantom power but only applies it globally to both channels (i.e. if its on for mic one, it's on for mic 2). If I have it on and connect a non-phantom mic (SM57) to the interface, will it fuck things up in some way? Will it work?

Dynamic mics don't give a shit about phantom- a 57 will be a-ok. Generally speaking though it's best to physically connect any mic with phantom off and turn phantom on with the mic(s) connected. Reverse the process when unplugging. Hot swapping is technically ok but the most stressful thing you can do to the system- avoid if possible.
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Re: Little tech questions from your day

Postby Dr Tony Balls on Mon Jan 07, 2019 12:59 pm

Thanks, yall!
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Re: Little tech questions from your day

Postby bassdriver on Sat Jan 12, 2019 11:51 am

If I wanted to balance the output of a Studer 169 channel strip, can I just get a simple 1:1 line transformer such as the monacor LTR-110

https://www.monacor.de/produkte/beschal ... g/ltr-110/

or something like a Edcor WSM600/600?

would that work or would I need to add a circuit to drive an OT? there’s some talk about this on Gearslutz, but mostly about a balanced direct out pre fader,
while I would balance the signal post fader.
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Re: Little tech questions from your day

Postby Adam P on Sat Jan 12, 2019 5:24 pm

I would think a simple 1:1 transformer should work. The transformer primary should present the same load as it would see without the transformer.

If you wanted to be super-simple about it you could impedance-balance.
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Re: Little tech questions from your day

Postby bassdriver on Sun Jan 13, 2019 12:12 pm

Adam P wrote:I would think a simple 1:1 transformer should work. The transformer primary should present the same load as it would see without the transformer.

If you wanted to be super-simple about it you could impedance-balance.


thanks. haven't thought of impedance balancing it, but that would of course be the cheapest version. I'll try that!
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Re: Little tech questions from your day

Postby Nate Dort on Sun Jan 13, 2019 2:15 pm

bassdriver wrote:
Adam P wrote:I would think a simple 1:1 transformer should work. The transformer primary should present the same load as it would see without the transformer.

If you wanted to be super-simple about it you could impedance-balance.


thanks. haven't thought of impedance balancing it, but that would of course be the cheapest version. I'll try that!


Is there a reason you need to balance it at all? Is it a long run or something?
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Re: Little tech questions from your day

Postby bassdriver on Mon Jan 14, 2019 12:28 pm

Nate Dort wrote:
bassdriver wrote:
Adam P wrote:I would think a simple 1:1 transformer should work. The transformer primary should present the same load as it would see without the transformer.

If you wanted to be super-simple about it you could impedance-balance.


thanks. haven't thought of impedance balancing it, but that would of course be the cheapest version. I'll try that!


Is there a reason you need to balance it at all? Is it a long run or something?


Not really, I guess. Thing is, I sold my racked Studer 900 stereo channel and now the buyer asked if I would rack some 169 channels for him. Including XLR connectors and balancing. He runs a mobile studio, so I assume there will not be any long cable runs from preamps to the interface.

In case he agrees on unbalanced XLR outputs, would I simply connect pin 3 to ground?
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Re: Little tech questions from your day

Postby TomWanderer on Mon Jan 14, 2019 2:29 pm

I've got an MXR Commande series phaser that needs an ac adapter solution. It has the 1/8" plug style input for the supply and I see you can get a handy little 1/8" converter to put at the end of a standard power supply...I'm just wondering if anyone knows if the tip is supposed to be positive or negative on the MXR Commande stuff. Any help would be greatly appreciated.
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Re: Little tech questions from your day

Postby Tommy on Mon Jan 14, 2019 3:43 pm

TomWanderer wrote:I've got an MXR Commande series phaser that needs an ac adapter solution. It has the 1/8" plug style input for the supply and I see you can get a handy little 1/8" converter to put at the end of a standard power supply...I'm just wondering if anyone knows if the tip is supposed to be positive or negative on the MXR Commande stuff. Any help would be greatly appreciated.


The regular MXR stuff that used 1/8" (and Proco Rat, EHX, etc.) is tip positive, so I'd guess tip positive.
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