Hitachi V 1565 100Mhz Scope

[Philbywhizz]

(I hope this is the right forum for this post).
First a bit of background:

I'm an electronics newbie - no formal training, all self taught. I've been dabbling a little, but have only started to get serious in my hobby in the last couple of months. My first original scope was a Dick Smith special (Q1803 10Mhz 1Ch) which when I first bought on eBay about 12 months ago (<$50 from memory). I knew it was limited in what it could do, and at the time I just couldn't find a higher bandwidth scope for a cheap price. I just wanted to play with a scope and see what it could do with it. At the time I thought "I wouldn't need anything faster than 10Mhz because I'm only playing with 1Mhz signals" (This is before I knew what the bandwidth meant). "I'm playing with digital arena anyway". I tried to use it a couple of times, but I couldn't really get any meaningful information out of it (I could get nothing new than my multi-meter would give me). I then stuck it on a shelf and it collected dust. Scopes are useless to me.

I.. was.. so.. so.. wrong..

Last week, after getting a little frustrated why some of my circuit ideas weren't working as I expected, I decided to find a better scope - I came across a dual channel Hitachi V 1656 2Ch 100Mhz scope on eBay (around $80) and figured I can't afford a fancy Rigol DSO scope, I'll try and grab this and see what the fuss is about.

I was a little worried that maybe it wouldn't work. For $80 surely something would be broken, a dial missing, etc.. The scope came with no probes or power cables, but after playing with all the settings on the scope and trying different things to test each setting (I used my 60Mhz probe from my Q1803 - so hopefully that will be ok still), everything appears to be working - Bonza!! It even has a calibration sticker on the side.

This beast has so many features that my little Q1803 didn't have. I'm going to have to learn some of these extra functions (like the delay and hold-off settings).

I just wanted to say that Dave's video (#86) on "Get an analog scope for under $50" still rings true today (ok, add a little for inflation - its a 5 year old video). I don't know if I just got lucky, or maybe $80 is way too much. Either way I've just spent the past few hours just playing with the scope and actually saying out loud 'wow' when I can see the extra ringing on my 1Mhz square wave which my old scope didn't show. It also shows my clock signal 'echoing' into a ground signal. None of this I could see with my old Q1803. I can already see a new world so I've already got my money's worth!

Because I have 2 channels now,  do I need to use a 100Mhz probe on a 100Mhz scope? I assuming that I already have a 60Mhz probe from my Q1803 the scope's bandwidth would be limited to that. To get the full 100Mhz I need a 100Mhz or greater probe?

And while I'm on getting another probe - how does the ext-trigger connected up? Is that just another probe connected to it?

[med6753]

That is a nice scope! Looks brand new. Definite good score!  I've never personally used an Hitachi scope but I've heard good things about them. If you haven't already I would scrounge up an operator's manual and service manual. I'm sure they must be available somewhere.

Because I have 2 channels now,  do I need to use a 100Mhz probe on a 100Mhz scope? I assuming that I already have a 60Mhz probe from my Q1803 the scope's bandwidth would be limited to that. To get the full 100Mhz I need a 100Mhz or greater probe?

And while I'm on getting another probe - how does the ext-trigger connected up? Is that just another probe connected to it?

That depends. If you intend on measuring signals utilizing the scopes full B/W then yes, you need probes equal to or better than 100 Mhz. If you are measuring signals less than your current 60 Mhz probes then they will be fine. Invest in the best probes you can if you decide to get new ones. Search the blog for suggestions.

The external trigger is for using a signal source external to the scope for locking in an applied signal. It's not used much but it can come in handy.

[Philbywhizz]

That is a nice scope! Looks brand new. Definite good score!  I've never personally used an Hitachi scope but I've heard good things about them. If you haven't already I would scrounge up an operator's manual and service manual. I'm sure they must be available somewhere.

I've managed to find an operator's manual - still looking for a service manual, but I'm not too concerned. I'd be a little scared to open up the cover and poke around because I don't know what I'm doing. At least I now know what all the buttons and dials do.

[Performa01]

A scope probe is specified for some upper frequency limit, but that doesn't mean it acts like a low-pass filter and attenuate everything above that frequency. Quite the opposite might be true. There is juat no guarantee on the frequency response above the specified frequency limit and the deviations might well exceed +/- 3dB.

In short, your 60MHz probe might well show you all frequencies up to the scope's bandwidth limit, but it probably won't show you the truth, e.g. more or less overshoot/ringing than what is actually there.

Apart from that, one of the main applications for a scope is to see the time relation between different signals, hence we need at least two channels and single channel scopes are pretty much a visualisation tool for beginners only.
To fulfill this task, the two channels have to be identical in timing behaviour, which of course includes the probes.
So it is only natural to equip all channels with identical probes. Get some 150MHz rated probes, they are still affordable, even though three of them might be close to what you've paid for your scope.

The trigger channel usually has the same input characteristic as the regular channels, so it is perfectly valid to use a probe here as well, especially if you want to trigger from a higher impedance circuit node.

Btw, this is a real nice scope in apparently mint condition you've got here. Hitachi used to make very nice scopes.

[Brumby]

A scope probe is specified for some upper frequency limit, but that doesn't mean it acts like a low-pass filter and attenuate everything above that frequency. Quite the opposite might be true. There is juat no guarantee on the frequency response above the specified frequency limit and the deviations might well exceed +/- 3dB.

In short, your 60MHz probe might well show you all frequencies up to the scope's bandwidth limit, but it probably won't show you the truth, e.g. more or less overshoot/ringing than what is actually there.

This is very true and I remember the first time I used this - a very long time ago......

I was given a 27Mhz radio controlled toy to check out and all I had available was my 15MHz Hitachi scope and a multimeter.  I was able to check the transmitter output by feeding it to the scope - and I was able to see the pulse position modulation change as I operated various controls on the transmitter.  The level was down - but the timing was measurable.  It provided very useful information despite the signal being nearly double the figure stamped on the scope.

[Philbywhizz]

In short, your 60MHz probe might well show you all frequencies up to the scope's bandwidth limit, but it probably won't show you the truth, e.g. more or less overshoot/ringing than what is actually there.

I suspected this was the case - and it is nice to know that my thoughts appear to be correct here.

Apart from that, one of the main applications for a scope is to see the time relation between different signals, hence we need at least two channels and single channel scopes are pretty much a visualisation tool for beginners only.
To fulfill this task, the two channels have to be identical in timing behaviour, which of course includes the probes.
So it is only natural to equip all channels with identical probes. Get some 150MHz rated probes, they are still affordable, even though three of them might be close to what you've paid for your scope.

I'm adding some new probes to the top of my wish list, as I only have one right now (from my old scope). Thanks for the advice (on getting 3).

[edavid]

A scope probe is specified for some upper frequency limit, but that doesn't mean it acts like a low-pass filter and attenuate everything above that frequency. Quite the opposite might be true. There is juat no guarantee on the frequency response above the specified frequency limit and the deviations might well exceed +/- 3dB.

I disagree with this.  A scope probe which did not have a smooth rolloff in the frequency domain would introduce unacceptable aberrations in the time domain.  So, scope probes are never designed that way.

Of course you can get frequency response bumps from the inductance of the ground lead, with any probe.

And to the OP, you can just buy a pair of (cheap) 100MHz probes, and save your 60MHz probe for the rare occasions when you need to use the external trigger.

[tggzzz]

Either way I've just spent the past few hours just playing with the scope and actually saying out loud 'wow' when I can see the extra ringing on my 1Mhz square wave which my old scope didn't show. It also shows my clock signal 'echoing' into a ground signal. None of this I could see with my old Q1803. I can already see a new world so I've already got my money's worth!

Probing technique becomes vital at those frequencies. Consider that 6" ground probe lead is ~150nH, and that the input capacitance is ~15pF, and then calculate the resonant frequency.

See https://entertaininghacks.wordpress.com/2015/04/23/scope-probe-accessory-improves-signal-fidelity/ for the practical effects, and https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/ for solid background information including theory and practical techniques.

Because I have 2 channels now,  do I need to use a 100Mhz probe on a 100Mhz scope? I assuming that I already have a 60Mhz probe from my Q1803 the scope's bandwidth would be limited to that. To get the full 100Mhz I need a 100Mhz or greater probe?

Greater.

Somewhat simplistically, the composite risetime is sqrt(sum of squares).