Equip your electronics bench- Help!!!

[finom1]

At the time of the Beatles, I was making guitar amplifiers for a group of rock musicians.

I had a very simple and basic measurement equipment because this kind of amplifiers is not demanding.

It is precisely this lack of quality and performance that did, and still do, that these amplifiers have a different sound from that of modern transistors amplifiers.

Wanting to make better amplifiers (distortion and bandwidth) is exactly the mistake not to do.

Why use a completely outdated technology if it is to try to do the same as a 50 bucks actual amplifier "made in PRC" ?

If you want to be consistent, one must use the same measuring devices as those employed at the time.

There is moreover an advantage in that: the tubes measuring devices were much reliable for use with circuits where there were very high voltages (several hundred volts), whereas modern devices are not provided for such accidental overloads.

Of course, you can also use updated high end measuring equipments.

But that does not respect the philosophy and purpose of your project.

Regarding the purchase of these old measuring equipment, you must have patience and look for bargains.

You can certainly buy at very low prices or even get them for free.

The more expensive item is probably the tube tester...(about 200 US§)

NB: the scope I used in this time was a heathkit io-12e....NOT A RIGOL DS1054Z...

What I had in this time:

Sine square wave generator
http://www.radiomuseum.org/r/mble_bem004_bem_004.html

Multimeters
http://www.radiomuseum.org/r/hioki_multimeter_af105.html
http://www.radiomuseum.org/r/hansen_multimeter_uv_47.html
http://www.radiomuseum.org/r/avo_universal_avometer_8_mk_i.html

Oscilloscope
http://www.radiomuseum.org/r/heath_laboratory_oscilloscope_i.html

Hello Oldway,
I only wished I lived close by you. You have been through the quest we are just starting on!!! My wife makes a killer "cheese cake" that I could bring over for you. Listening to your experiences will keep us safe and speed our way through some great projects for kids. That is our mission, to help inspire young people to have fun with electronics. To put there minds on leaning, educating them while having fun. We believe this will make better memories for them, compared to whats going on in the world today. I had fun as a kid and was always excited to find out how things worked. We would like to provide a place for kids to come over a learn at their own pace, opening their minds to the possibilities that life has to offer. We will post here a & make youtube videos as examples.

Please see the response we made to R005T3r, about what our goals are for setting up a working test bench for our Guitar Amplifier Projects.

I hope reading it will inspire you to again share the specifics of what type of equipment & models if possible would be best for us to achieve our goal.

Oldway, we want to show respect by waiting and finding the best value in our purchases. I big problem became evident when assessing our repair skills at this time. That will mean spending more money for test equipment that is working and has been tested! I hope you understand our problem with lack of experience and knowledge at this time in life.

Respectfully,
finom1 & son

[oldway]

Thank you for your kindness and sympathy.

I would gladly help you, but I live in Europe, it's a bit far from the USA ....

I remind you that the voltages in a guitar amplifier are very high (up to 800V) and there is a serious risk of working on these tube amplifiers.

It is not recommended for a beginner, much less for a kid.

If you buy your measuring instruments with care, you should not spend more than a few hundreds US§.

This old tube measuring instruments are usually very simple and easy to repair.
So do not be afraid to buy a faulty instrument, this will increase your experience.
At worst, you get help from a friend or on this forum.

I wish you great success in your projects.

NB: about analog multimeters....great video as al the Dave's videos. 

[R005T3r]

Alright, well, this clarify a lot of things, and changes a lot tools to add in  your collection, also.

When you are dealing with audio, especially antique things you will need:
1. tube/valve tester
2. a decent soundcard + pc : it will became handy because when you actually fix things up, you can record thing up and monitor the levels. It will also give you a clear idea on what the problem may be. Also, if you are going to change the tubes and valves and stuff, you can see the difference.
3. a multi meter. A decent one. You are dealing with HV and you must not be cheap, otherwise you end up killing yourself.
4. a good/solid power supply: vintage always equals to more power consumption, and nasty voltages. Better be ready, since you don't know what kind of stuff you are going to test...
5. an oscilloscope. a basic oscilloscope would do most of your jobs. Take a combiscope 20Mhz, it's not that much and you won't regret it.No need of digital things.
6. an audio spectrum analyzer may be handy in some few situations (that's why I don't recommend it), but there's even something better for the price, see after...
7. mains filter. When you are working with the audio spectrum, low (0-200 Hz) lead to mains interference, menaing you will hear hums...
8. an audio signal generator. This may be very tricky to find. See after.

So, whenever you are dealing with HV, you MUST not be cheap on instruments, and you can't trust a 100 usd multimeter. Better considering a good one instead, security first.
As a reguard for power supply, anyway, take something at least 5A rated, I can't tell which voltages tought: never used valves, but 30/60V may be a good range... Also, take a mains isolated one.
As a reguard to mains filtering: yes, you will need some kind of filtering otherwise you may add the hum problems on your device under test (or restoration)
As for audio signal generators, you need something very specific, and even if the device is in specs it don't mean it sounds good... take something refurbished DC-250Khz... You won't need more, and it have to be very precise and low distortion.
As a reguard for the oscilloscope, if you don't like analogs and you want digitals take a basic one, don't spend too much since it's not worth it.

The most fitting solution to your needs instead of a spectrum analyzer or instruments of any kind exept your multimeter may well be an audio analyzer or a signal analyzer (better if specific for audio), like this units here:
http://www.ebay.com/itm/Panasonic-VP-7723A-5Hz-100KHz-0-0005-Audio-Analyzer-/380403386509
http://www.datatron.it/user/articoli.php?op=det&id=624

Don't forget that if you want to spend more, there's this one:
U8903A Audio Analyzer : http://www.keysight.com/en/pcx-x205218/audio-analyzers?nid=-32511.0.00&cc=IT&lc=en
and it's $14.000 (that's not much, considered that a decent spectrum analyzer is well over $20K), however, this is an example. You can find a lot of old stuff that it's more suited to the technology you are dealing with...

[Paul Price]

I don't get it. It's like everyone is set on encouraging you to build your own NASA facility to get a kid's rubber-band powered airplane tested.

First of all, the cool sound is best when distorted, so why bother with clean output when the kids are going to add fuzz pedals to feed their guitar amps a distorted signal anyway.

All you need to do is install a phone plug on the amps you have already working and let the kids rock out!

Buy yourself a cheap 2-channel analog oscilloscope and a used multimeter at a local HamFest,  flea market, or ebay and you are in business!

You don't need a Distortion Analyzer, just get to know how to use an oscilloscope.
With the purchase of a small solderless breadboard, one quad-opamp and a few resistors and capacitors you can easily create a high quality sinewave test signal for testing power smplifiers, total cost only a buck or two or maybe nothing (if you salvage parts from a discarded piece of home electronics equipment.)

With the input signal to the amp on the first oscilloscope channel and the inverted output of the amplifier on the second channel, you can adj. the variable gain on one vertical channel to cancel out the input signal..what is left that doesn't cancel out is the distortion part of the output. It is a simple as that. You can use automotive taillight incandescent bulbs for a high-power load for testing.

If you spend more than $100 to start playing around with electronics then you are just wasting money.

[ez24]

I don't get it. It's like everyone is set on encouraging you to build your own NASA facility to get a kid's rubber-band powered airplane tested.

SOP   

[finom1]

Alright, well, this clarify a lot of things, and changes a lot tools to add in  your collection, also.

When you are dealing with audio, especially antique things you will need:
1. tube/valve tester
2. a decent soundcard + pc : it will became handy because when you actually fix things up, you can record thing up and monitor the levels. It will also give you a clear idea on what the problem may be. Also, if you are going to change the tubes and valves and stuff, you can see the difference.
3. a multi meter. A decent one. You are dealing with HV and you must not be cheap, otherwise you end up killing yourself.
4. a good/solid power supply: vintage always equals to more power consumption, and nasty voltages. Better be ready, since you don't know what kind of stuff you are going to test...
5. an oscilloscope. a basic oscilloscope would do most of your jobs. Take a combiscope 20Mhz, it's not that much and you won't regret it.No need of digital things.
6. an audio spectrum analyzer may be handy in some few situations (that's why I don't recommend it), but there's even something better for the price, see after...
7. mains filter. When you are working with the audio spectrum, low (0-200 Hz) lead to mains interference, menaing you will hear hums...
8. an audio signal generator. This may be very tricky to find. See after.

So, whenever you are dealing with HV, you MUST not be cheap on instruments, and you can't trust a 100 usd multimeter. Better considering a good one instead, security first.
As a reguard for power supply, anyway, take something at least 5A rated, I can't tell which voltages tought: never used valves, but 30/60V may be a good range... Also, take a mains isolated one.
As a reguard to mains filtering: yes, you will need some kind of filtering otherwise you may add the hum problems on your device under test (or restoration)
As for audio signal generators, you need something very specific, and even if the device is in specs it don't mean it sounds good... take something refurbished DC-250Khz... You won't need more, and it have to be very precise and low distortion.
As a reguard for the oscilloscope, if you don't like analogs and you want digitals take a basic one, don't spend too much since it's not worth it.

The most fitting solution to your needs instead of a spectrum analyzer or instruments of any kind exept your multimeter may well be an audio analyzer or a signal analyzer (better if specific for audio), like this units here:
http://www.ebay.com/itm/Panasonic-VP-7723A-5Hz-100KHz-0-0005-Audio-Analyzer-/380403386509
http://www.datatron.it/user/articoli.php?op=det&id=624

Don't forget that if you want to spend more, there's this one:
U8903A Audio Analyzer : http://www.keysight.com/en/pcx-x205218/audio-analyzers?nid=-32511.0.00&cc=IT&lc=en
and it's $14.000 (that's not much, considered that a decent spectrum analyzer is well over $20K), however, this is an example. You can find a lot of old stuff that it's more suited to the technology you are dealing with...

Right on point, thank you!

[rstofer]

Well, that leads up back to the analog versus digital scope debate which is endless!  There is a current version of the topic running around right now.

I like analog scopes but the features of the digital scope just make the scope so much more worthwhile.  I don't want a scope "for parts" or "couldn't test" and, all in, I guess I would rather have a new scope with a warranty - all things being equal.  If the budget can stand the DS1054Z then that's what I would do.  And I did...

I've came up with a combiscope oscilloscope, because NOW his best bet is to start actually doing some projects. So, instead of bugging out with what is the best instrument or what is the best "convenient" one, the OP should tell us what he's planning to do, what are his interests in electronics (I hardly doubt that he's interested in radars anymore). Are you intended to make only guitar amplifiers and other instrument-oriented projects? If so, an oscilloscope like the DS1054Z is useless  because you will never use it's full bandwidth.

I can't get to the part where having excess bandwidth is a bad thing and left to itself, the 1054Z is only a 50 MHz scope.  Sure, I like analog scopes and if the right one comes along, fine.  Something in the $200 or less range would be great.  If not, it's pretty nice to get a fully featured digital scope for $400, complete with a warranty.  A scope is a forever kind of thing.  Then too, there is no compelling reason to hack the thing just to get bandwidth and serial decoding if they are not going to be used.  OTOH, why not?  Get it while you can kind of thinking.

Of all the tools on the bench, the scope is probably the most important and the most useful.  It might be possible to follow the input through the amplifier with a V-O-M but it's a lot easier to do with a scope.  FWIW, I would note the voltage at a test point with the V-O-M BEFORE I touched it with a scope probe.  There are limits for the voltage input to scopes - even with a x10 probe.  Read the datasheet for the scope!

I would want the V-O-M but I could settle for a DMM even though the readings may be a bit high.  I could even settle for a $6 Harbor Freight DMM if I had to.  But I want a decent scope and I want to know that it works and, hopefully, will keep on working.  I'd be pretty careful probing high voltages with the Harbor Freight meter!  Maybe some low voltage gloves would be a good idea - low voltage being 600V and below, not 12V!

I have nothing but good things to say about my $200 Tek 485 350 MHz scope.  It's great and it comes from a family of scopes I have long admired.  But I got lucky when I bought it through eBay.  It worked and has kept on working for 12 years.  I'm not sure my experience is universal!  A non-functional analog scope doesn't even make a good boat anchor.

[finom1]

Well, that leads up back to the analog versus digital scope debate which is endless!  There is a current version of the topic running around right now.

I like analog scopes but the features of the digital scope just make the scope so much more worthwhile.  I don't want a scope "for parts" or "couldn't test" and, all in, I guess I would rather have a new scope with a warranty - all things being equal.  If the budget can stand the DS1054Z then that's what I would do.  And I did...

I've came up with a combiscope oscilloscope, because NOW his best bet is to start actually doing some projects. So, instead of bugging out with what is the best instrument or what is the best "convenient" one, the OP should tell us what he's planning to do, what are his interests in electronics (I hardly doubt that he's interested in radars anymore). Are you intended to make only guitar amplifiers and other instrument-oriented projects? If so, an oscilloscope like the DS1054Z is useless  because you will never use it's full bandwidth.

I can't get to the part where having excess bandwidth is a bad thing and left to itself, the 1054Z is only a 50 MHz scope.  Sure, I like analog scopes and if the right one comes along, fine.  Something in the $200 or less range would be great.  If not, it's pretty nice to get a fully featured digital scope for $400, complete with a warranty.  A scope is a forever kind of thing.  Then too, there is no compelling reason to hack the thing just to get bandwidth and serial decoding if they are not going to be used.  OTOH, why not?  Get it while you can kind of thinking.

Of all the tools on the bench, the scope is probably the most important and the most useful.  It might be possible to follow the input through the amplifier with a V-O-M but it's a lot easier to do with a scope.  FWIW, I would note the voltage at a test point with the V-O-M BEFORE I touched it with a scope probe.  There are limits for the voltage input to scopes - even with a x10 probe.  Read the datasheet for the scope!

I would want the V-O-M but I could settle for a DMM even though the readings may be a bit high.  I could even settle for a $6 Harbor Freight DMM if I had to.  But I want a decent scope and I want to know that it works and, hopefully, will keep on working.  I'd be pretty careful probing high voltages with the Harbor Freight meter!  Maybe some low voltage gloves would be a good idea - low voltage being 600V and below, not 12V!

I have nothing but good things to say about my $200 Tek 485 350 MHz scope.  It's great and it comes from a family of scopes I have long admired.  But I got lucky when I bought it through eBay.  It worked and has kept on working for 12 years.  I'm not sure my experience is universal!  A non-functional analog scope doesn't even make a good boat anchor.

Thank you for make good points on safety and long term value.

[rsjsouza]

I glanced over the thread and saw a few recommendations. I also agree that purchasing "the world" of equipment right now may not be the best idea, but several sensible options were provided. I will add a few.

I saw somewhere that a variac was needed. I purchased a Mastech one that has good quality (check here) and I have been using it since then without a glitch.

I drool over Krohn Hite oscillators for audio, but I haven't had the chance to get one yet. If you are looking for distortion measurements, look at eBay/craigslist for their 4400 series of ultra pure sinewave generators (one is here). I wouldn't jump to it from the get go, but it is surely a good model number to keep in your pocket if you ever feel the need to perform these types of measurements.

[deadlylover]

I'll also echo some of the suggestions where you don't need to build the perfect electronics work bench to get started, you can do a hell of a lot with just a soldering iron and a multimeter or two (and maybe a scope =P). You don't need an LCR meter to know a bulging cap is knocking on death's door for example (and if you're restoring old gear, you'll replace all the electrolytics anyway as a rule), so get stuck into it and have multiple projects on the table to stop everything stalling when you're waiting for a new piece of gear to come in.

Keep a lookout for broken equipment being sold for very cheap, even if you fail to repair them you can always salvage the parts and I think the educational value is priceless. Maybe start with pieces that have service manuals and schematics first.

For a scope you could go either way, get something cheap or get a 1054Z to act as your stable/reliable base. I'm sure you'll have no problems at all offloading the 1054Z for not too much loss in the future if you decide you don't need it anymore, so that's something to keep in mind.

The Panasonic audio analyser linked earlier and it's sister models might be all you'll ever need, some can measure distortion separately up to the 5th harmonic at the touch of a button. The VP-7722A I got for $300ish can measure down to -112dB (0.00023%) THD+N, @ 1khz/30khz BW 2Vrms, and I don't think you'll be making many tube amplifiers that can exceed that. To put that in perspective you need to spend 30 grand on the Audio Precision flagship to reach -120dB performance.
You'll have to be very patient and somewhat brave to get one as cheap as I did, perhaps it's not for the faint of heart if you have a set budget, but these old dogs will go head to head with any entry level or midrange analyser today in terms of residual distortion anyway.

[finom1]

I glanced over the thread and saw a few recommendations. I also agree that purchasing "the world" of equipment right now may not be the best idea, but several sensible options were provided. I will add a few.

I saw somewhere that a variac was needed. I purchased a Mastech one that has good quality (check here) and I have been using it since then without a glitch.

I drool over Krohn Hite oscillators for audio, but I haven't had the chance to get one yet. If you are looking for distortion measurements, look at eBay/craigslist for their 4400 series of ultra pure sinewave generators (one is here). I wouldn't jump to it from the get go, but it is surely a good model number to keep in your pocket if you ever feel the need to perform these types of measurements.

Thank you for sharing your ideas!

[finom1]

I'll also echo some of the suggestions where you don't need to build the perfect electronics work bench to get started, you can do a hell of a lot with just a soldering iron and a multimeter or two (and maybe a scope =P). You don't need an LCR meter to know a bulging cap is knocking on death's door for example (and if you're restoring old gear, you'll replace all the electrolytics anyway as a rule), so get stuck into it and have multiple projects on the table to stop everything stalling when you're waiting for a new piece of gear to come in.

Keep a lookout for broken equipment being sold for very cheap, even if you fail to repair them you can always salvage the parts and I think the educational value is priceless. Maybe start with pieces that have service manuals and schematics first.

For a scope you could go either way, get something cheap or get a 1054Z to act as your stable/reliable base. I'm sure you'll have no problems at all offloading the 1054Z for not too much loss in the future if you decide you don't need it anymore, so that's something to keep in mind.

The Panasonic audio analyser linked earlier and it's sister models might be all you'll ever need, some can measure distortion separately up to the 5th harmonic at the touch of a button. The VP-7722A I got for $300ish can measure down to -112dB (0.00023%) THD+N, @ 1khz/30khz BW 2Vrms, and I don't think you'll be making many tube amplifiers that can exceed that. To put that in perspective you need to spend 30 grand on the Audio Precision flagship to reach -120dB performance.
You'll have to be very patient and somewhat brave to get one as cheap as I did, perhaps it's not for the faint of heart if you have a set budget, but these old dogs will go head to head with any entry level or midrange analyser today in terms of residual distortion anyway.

Thank you for sharing your ideas!

[KL27x]

Buying stuff doesn't make you learn by osmosis. It is not like you're opening a shop to manufacture/test/repair X product, and want to outfit it with stuff the techs you will hire might need.

You want to make cigar box amplifiers for your kids. Yourself. If you need to ask us, you might as well save your money. If you just want a good cover to show the wife you're busy, buy a power supply, DMM, scope, and a soldering iron.

[oldway]

You should first make a list of the measurements and tests you will need to do and specify what the precision level you need.
Using a modern DSO on high voltage circuits as encountered in guitar tube amplifiers is not a good idea.
Risk to blow up the analog front end is high.

[finom1]

You should first make a list of the measurements and tests you will need to do and specify what the precision level you need.
Using a modern DSO on high voltage circuits as encountered in guitar tube amplifiers is not a good idea.
Risk to blow up the analog front end is high.

Hello oldway,
I sent you a message did you get it. I asked about a choice of specific meters that I would like to buy now.

Thank you.

[finom1]

OK, made our first purchase today:
Simpson 270-5RT Extra-High Accuracy Analog Multimeter - http://www.ebay.com/itm/122036060298

Thank you oldway!

Oscilloscope is next in line.

Thanks  everyone for your ideas.

[rstofer]

OK, made our first purchase today:
Simpson 270-5RT Extra-High Accuracy Analog Multimeter - http://www.ebay.com/itm/122036060298

Great choice!

You might look into x100 scope probes if you want to work on tube type equipment.  With a x10 probe you are only allowed to go up to 300 Vrms on the DS1054Z.  A little cushion would be nice.  It's easy to set the scope for 1x, 10x, 100x or even 1000x plus some other built-in values.

[finom1]

Hello,
could you please provide a link to the very best test & accessories probes to protect test scope up to 1000 volts? I will be strictly working on tube amps. I picked up two vintage radios with giant tube amps in them.

Looking forward to input to keep this type of investment safe!!!

Thanks

[oldway]

Simply, do not buy an expensive oscilloscope.
Stay in the range 50 to 100 US§

Modern oscilloscopes are not designed to work on high voltages such as there is in guitar amplifiers. ( Rigol 10V/div, Tektronix 465 50V/div)

When you have burned the front end input stage of your Rigol 1054Z, you will understand what I mean ....
How will you fix it?
How much the repair is going to cost you?

You are a beginner, you will make mistakes, that's normal.

[rstofer]

Hello,
could you please provide a link to the very best test & accessories probes to protect test scope up to 1000 volts? I will be strictly working on tube amps. I picked up two vintage radios with giant tube amps in them.

Looking forward to input to keep this type of investment safe!!!

Thanks

The best probes will be Tektronix and they run about $500 EACH!
https://www.amazon.com/Tektronix-P5100A-Passive-Voltage-Length/dp/B005K0M45O

I would be looking for something a LOT cheaper because the frequencies involved aren't very high.  All we really need is a probe with a 99 MOhm impedance instead of 9 MOhm for the x10 probe.
Something like:

http://www.all-spec.com/Catalog/Test-Measurement/Oscilloscopes-Accessories/Oscilloscope-Probes/5827A-19816?utm_source=bing&utm_medium=cpc&utm_campaign=Product%20Listing%20Ads%20-%20Shopping&utm_term=1100400298755&utm_content=PLA

http://www.aliexpress.com/store/product/P4100-High-Voltage-Oscilloscope-Probe-2KV-100-1-100MHz-Alligator-Clip-Test-Probe/608349_32482963758.html

[R005T3r]

Nah, just take a look at this ones:
http://uk.rs-online.com/web/p/oscilloscope-probes/7296655/    : they are 2000V rated and they are fine, also not that expensive.

I hardly doubt these would be any good for your pourpouse:
http://uk.rs-online.com/web/p/oscilloscope-probes/3669141/   : they are rated 15KV. Last time I've seen one of these was at a transformer factory.

[ez24]

http://www.aliexpress.com/store/product/P4100-High-Voltage-Oscilloscope-Probe-2KV-100-1-100MHz-Alligator-Clip-Test-Probe/608349_32482963758.html

You might want to give Aliexpress a try.  Seems to be the best place to buy electronics related stuff.
Going to start a new topic about them

[R005T3r]

http://www.aliexpress.com/store/product/P4100-High-Voltage-Oscilloscope-Probe-2KV-100-1-100MHz-Alligator-Clip-Test-Probe/608349_32482963758.html

You might want to give Aliexpress a try.  Seems to be the best place to buy electronics related stuff.
Going to start a new topic about them

NO, it's not at all the best place to buy instrumentations, especially security rated probes. Man, you are working in a possibly HV envoriment. It's like having a black mamba on a stick and you wear lattex gloves. Don't do that, spend more but be safe!

[oldway]

Look at this interesting video "restoration video" to understand how important it is to have a capacitor analyser with leakage test.
https://www.eevblog.com/forum/projects/1959-gibson-gibsonette-repair/

NB: he is using a capacitor checker Heathkit IT-11
http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_IT-NE/IT-11/IT-11.pdf

[nanofrog]

Hello,
could you please provide a link to the very best test & accessories probes to protect test scope up to 1000 volts? I will be strictly working on tube amps. I picked up two vintage radios with giant tube amps in them.

Looking forward to input to keep this type of investment safe!!!

Thanks

As mentioned, oscilloscopes aren't designed to take high voltages. You'd want to use say a 100x probe vs. a 1x or 10x. Given the bandwidth requirement isn't that demanding, you'd be able to find these relatively inexpensively as well. 

For example: 100x 2KV High Voltage Oscilloscope Probe 100MHz. Not expensive at all.