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PostPosted: 22 Feb 2017, 11:40 
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When given a choice at the same approximate cost, go with the Tek.

MAKE SURE that it works and/or you have a no-cost return option if it does not.


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PostPosted: 22 Feb 2017, 17:36 
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Hi, The voltage rating is a bit misleading. I use ones with 30 volt ratings....but the probes are 1 to 1 and 1 to 10 and 1 to 100. So the probe does the reduction. I also personally like scopes that are PC based. They tend to give you more information than stand alone ones will. Any of the ones previously mentioned will do the job though. A feature that I consider essential is the ability to display a spectrum analysis of the input. It is invaluable in finding things like oscillations, noise, hum, and harmonic distortion products.

Good listening
Bruce

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PostPosted: 23 Feb 2017, 17:09 
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Thanks for suggestions! I have guaranteed (to some extent) return policy in case of HP, but not so in case of those Tektronix offers - hence my hesitation - no way of verifying their condition.
Thank You gofar for pointing out probe role! I didn't thought of that. So probe can "scale down" high voltage input to o-scope acceptable level while proportionally retaining signal "shape" and measured properties?
So one more thing is bandwidth. Most scopes claim to operate on frequencies measured in Mhz (30, 60, 100 and more) but since we are interested in frequencies of human audible range up to ~20Khz (~100Khz headroom according to "5 times rule" I've read somewhere about) does it mean that even lowest Mhz scope is plenty enough for my needs?


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PostPosted: 24 Feb 2017, 07:05 
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For audio work, 100mhz is more than enough. If you want to do FM tuner work, 200 - 300 is better.


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PostPosted: 11 May 2017, 06:28 
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Hi again! There was a discussion on variac-iso order ilustrated by this schematic (borrowed from EEV blog):
Attachment:
ISO_Variac.jpg

I did some more research on that Heathkit variac of Yours and there is also interesting "combo" built by "Mr Carlson" (YT channel):
Attachment:
variac-iso-dim_bulb-combo1.jpg

Attachment:
variac-iso-dim_bulb-combo.jpg


IP5220 schematic:
Attachment:
IP-5220.jpg


Both designs seem to use the same "variac first" logic (variant "B" from first attachment) so that's the way I'm going to take.
The only difference is presence of grounding in 5220 schematic on output outlets. I thought lack of such grounding is the entire idea of isolation transformer.
Now please explain politely what I didn't understand :D


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PostPosted: 10 Jun 2017, 22:14 
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good God, what are we all embarking on here!!!!!!


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PostPosted: 11 Jun 2017, 03:31 
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steakhead wrote:
good God, what are we all embarking on here!!!!!!


+1

Is this build an amplifier or buy as much test equipment as possible.

Perhaps I have the wrong idea, but I hope this isn't I want a calculator for my college course but the one I bought is to complicated and I don't know how to use it..

Just think of all the audio stuff you could build, but now I have a room full of test gear that I would only use once but I can't afford to build anything now..

Anyway best of luck with your delayed build, why not just build a kit?
Or do you intend to design from scratch.

As far as I'm concerned you just need a 25W soldering iron, a good meter something like a fluke, the ability to read a circuit and enough safety understanding not to get fried.<<if you don't have that forget the rest. :D

High voltage is dangerous, high capacitance with high voltage is lethal.
If you try to design an esoteric design for a first build you may end up with very expensive pile of junk.
However each to their own anyone trying to build something like Ongaku as a first project is a bit nuts, but that's just my opinion.

NB test equipment doesn't make you safe it complicates the issue and its very easy to make mistakes if you don't know what you are doing. Again just my opinion. KISS keep it simple and safe..its not off until its dead<< :D
Anyway have fun. Exit stage left..

Regards
M. Gregg

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PostPosted: 14 Jun 2017, 06:35 
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Mpffffff..... sometimes people build things because they can. Sometimes people build things because that is what (all) they have.

We just got back from a trip to Cuba - and saw a great deal of the latter. Some of it remarkable, clever and creative. Some of it dangerously crude.

Writing entirely for myself, I tend to look for equipment that is inherently safe, takes up no more real-estate than it must, and is fairly intuitive in its operation. The picture suggests something from a vintage monster-movie set, not something designed for safe, every day use. That it does include the basics of an isolation transformer, Variac and dim-bulb tester is all to the good, but the exposed connections - not so much.

Supporting my prejudices are the facts we have four grandchildren, all old enough to know better, but they still occasionally visit the 'radio room', two cats and two dogs. One of the cats (the one in the picture) *will* observe operations on the workbench if there is room. So, I am a bit more sensitive to bench safety than some.


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PostPosted: 14 Jun 2017, 10:08 
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Regarding people and pets,

That's one of the reasons I always fit discharge resistors to power supplies.
After you switch off and leave the room that's when little fingers start poking bits of hair clips and bare wire into air vents of equipment.
Valves with Anodes at potential after power off..It even caught me out with some friends equipment it had been off for almost a day and he opened it up. I looked inside and said that capacitor should have a discharge resistor, where he said, across here look :hot: ZAP :eek: did you get a shock he said...you could say that as I picked the coffee cup off the floor.
We get so complacent when power tubes pull the PSU down after power off. But if the heaters fail then we open the equipment and assume its dead because it always has been before..if it can happen it will happen. The same thing happens if you power up equipment with the power tubes removed then switch off.. :D Old equipment is a PITA for it. Even a trickle discharge is better than nothing 500K etc. (current/voltage dependent) On valve rectification just watch you don't exceed rectifier current max.

Regards
M. Gregg

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PostPosted: 14 Jun 2017, 17:14 
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My helpers are far to helpful. I make only fully enclosed gear.

Good listening
Bruce
Attachment:
My helpers 2.jpg


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