Author Topic: My $50 scope (Hung Chang) Tenma 72-720 [Inside Photos!]  (Read 25161 times)

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Offline elliott

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #25 on: August 07, 2013, 11:20:14 am »
OMG this HAS to be the ugliest oscilloscope EVER!



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I have one in black under the B&K name.
 

Offline mzacharias

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #26 on: August 07, 2013, 12:00:37 pm »
I had an older version B&K 2125 with component tester. Maybe similar late 80's to early 90's vintage. A real piece of Taiwanese crap. Built like a cheap boom box. I had bought it new at a time before eBay, and this was available from a local supplier.

Works OK at present, ( it's back in a corner of the shop) but in the past I have had to clean the controls several times, it developed a bad horizontal deflection transistor (open circuit emitter-base), a bad resistor in the focus circuit, and numerous bad solder connections, all in a scope that didn't really get used a terrible lot as these things go. The main board suffers from large areas of overheated components.

The Japanese (Kenwood) B&K's are much better.

I had a B&K 2190A (I think) basic 100mHz that was obviously a Goldstar and made in Korea. Decent basic performance, clean pacific rim type layout inside, no overheated components, and very reliable, but BORING. No fun to use; had a green trace, not the beautiful blue you get from a Tek with the blue filter.
 

Offline Stonent

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #27 on: August 07, 2013, 03:09:31 pm »
I think the black and red combination on scopes is just sexy.

I like the look of the newer black and red Uni-T scopes.
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Offline PA4TIM

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #28 on: August 07, 2013, 05:24:23 pm »
wow, that looks ugly and cheap from the inside. I scrapped a dead Heathkit from the 60's, that was tubes but the same type pcb.



as a contrast, the guts of a 1966 !! Tektronix. Thick goldplated pcbs. This is a 453, 50MHz scope, all transitors except two nuvistors
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Offline edy

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #29 on: August 10, 2013, 11:48:22 am »
OK, so I picked up one of these from Ebay as well, branded under the "JDR Model 2000" badge.

Looks like these are all the same:

Tenma 72-720
Elenco MO-1251
Hung Chang OS-620
Neotronics OS-620
JDR Model 2000

Looks like one of the cheapest CRO's around...Likely made by some OEM in Korea and bought by various small-time companies and rebranded to sell to Joe Public for cheap. There is a link to the original advertisement for JDR 2000 attached. Only $389.95 in 1987!!!!

So plugging in that value in http://www.dollartimes.com/calculators/inflation.htm revealed that "$389.95 in 1987 had the same buying power as $810.25 in 2013."  That would have been a cheap scope for that time, no? I'm sure it was built down to a price.

I found schematics here to download free PDF for the Hung Chang version:

http://elektrotanya.com/hung-chang_os-620_sch.pdf/download.html

So I just bought mine for $20 on Ebay... listing here:

eBay auction: #111134496460

Let's see how long this thing lasts.  ;) I've read on other forums that they weren't too reliable.
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Offline Stonent

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #30 on: August 10, 2013, 12:11:16 pm »
Finally someone bought one of the auctions I posted! I was really disappointed when those two Pintek scopes sold for $5.50 each to someone who didn't appear to be one of us.

Anyway mine seems to work ok. I got my probes in and the calibration signal seems to line up correctly with the screen.
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Offline edy

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #31 on: August 10, 2013, 12:33:14 pm »
I'll be getting it in a few weeks. I had it shipped to my parents in USA, but they are visiting me in a few weeks so they'll drive it up to Canada where I am.  Hopefully I won't need to fix anything and it will just work.

Dave was right, you can pick up a 20 Mhz scope for <$50, especially in the USA if you are willing to wait it out. And if you limit yourself to <$100 you can actually get even better deals on some good brand scopes. It'll be a good learning tool for any electronics student/hobbyist and it won't break the bank.

Yeah maybe they are limited these days, but a beginner like me would find it useful for viewing the characteristics of basic circuit designs/building blocks, testing components, etc. It is something fun to play with, either way.
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Offline Lightages

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #32 on: August 10, 2013, 01:05:34 pm »
I have one this scope in one of its incarnations. I have had mine since somewhere around 1992? It is still working well. Yes, it was one of the cheapest scopes available new at the time and it was my first scope.

I also have the full original manual, schematics, and calibration procedures. If anyone wants a copy I will scan and provide a link for download.
 

Offline Stonent

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #33 on: August 10, 2013, 01:33:23 pm »
I have one this scope in one of its incarnations. I have had mine since somewhere around 1992? It is still working well. Yes, it was one of the cheapest scopes available new at the time and it was my first scope.

I also have the full original manual, schematics, and calibration procedures. If anyone wants a copy I will scan and provide a link for download.

Well I've got the full Tenma manual. What brand was yours?
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Offline edy

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #34 on: August 10, 2013, 02:03:08 pm »
Thank you, a scan of the manual, schematics and calibration procedures would be amazing and much appreciated!!!

I have only been able to find schematics on the 35 Mhz version (JDR 3500 or Hung Chang OS-635), so I'm not sure if they are similar enough to the 20 Mhz version and it would be nice to know the parts in case something needs replacing.
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Offline Lightages

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #35 on: August 10, 2013, 02:06:43 pm »
A retailer in Canada was trying to sell this as their house brand "A-1 Electronics". They had removed the bezel with the original branding on it and copied the first page of the manual with their name on it. The original manufacturer is Hung Chang.
 

Offline Lightages

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #36 on: August 10, 2013, 02:07:22 pm »
Thank you, a scan of the manual, schematics and calibration procedures would be amazing and much appreciated!!!

I have only been able to find schematics on the 35 Mhz version (JDR 3500 or Hung Chang OS-635), so I'm not sure if they are similar enough to the 20 Mhz version and it would be nice to know the parts in case something needs replacing.

OK I will get on it over the next couple of days.
 

Offline Stonent

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #37 on: August 10, 2013, 02:22:22 pm »
Thank you, a scan of the manual, schematics and calibration procedures would be amazing and much appreciated!!!

I have only been able to find schematics on the 35 Mhz version (JDR 3500 or Hung Chang OS-635), so I'm not sure if they are similar enough to the 20 Mhz version and it would be nice to know the parts in case something needs replacing.

The manual is in the first post of this thread.
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Offline Lightages

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #38 on: August 10, 2013, 02:32:39 pm »
Yes that is right. I missed that for some reason. It is the same information that I have.
 

Offline Stonent

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Offline Stonent

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #40 on: August 10, 2013, 04:33:43 pm »
« Last Edit: August 11, 2013, 12:51:28 am by Stonent »
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Offline Stonent

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #41 on: August 10, 2013, 04:36:58 pm »
Even Tricky Dick got in on the action! Dick Smith Q-1240

« Last Edit: August 10, 2013, 04:39:14 pm by Stonent »
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Offline Stonent

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #42 on: August 10, 2013, 04:42:04 pm »
Wait, what's this from 2004?

http://www.electronicspoint.com/dick-smith-scope-t131532.html

Quote
I sent an email to "David L.Jones" and he kindly replied saying "
Hi Phil,
That is a spitting image of the (in)famous HungChang 20MHz scope. It is
probably the most re-badged scope in history! (it's an OK scope though!)
Sorry, can't remember off my head the exact HungChang model number or the
other brands it was re-badged under."

Hmm. Dave Jones... The name sounds familiar.

https://groups.google.com/forum/#!topic/aus.electronics/L64ccLS8phc

Even 2003...

Quote
Don't know that particular model (but most probably the typical 20MHz
cheapie), but Hung Chang are basically the cheapest nastiest scope you
can get. Haven't looked at them these days though, so don't know what
they are like now.
The same scope is (or was) rebadged under various brands.

Is it "descent" scope? - NO, Hung Chang's are bottom of the quality
scale.

But hey, it'll probably work fine, depending on what you want it
for...

Dave :)

https://groups.google.com/forum/#!searchin/aus.electronics/Hung$20Chang/aus.electronics/-QWidhOvlSk/51ZUmx56DgIJ

Quote from: David L. Jones
If memory serves me rightly, the Aron BS-601 is a basic 20MHz dual
trace unit, rebadged under half a dozen different names including Hung
Chang.
It's worth anywhere from $0 (some people give these away for free) to
maybe $150. $200 if it's as-new with probes maybe.

Dave :)



I just keep collecting these pictures!

Thanks Dave!



« Last Edit: August 10, 2013, 05:32:56 pm by Stonent »
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Offline amyk

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Re: My $50 scope Tenma 72-720 [Inside Photos!]
« Reply #43 on: August 10, 2013, 09:17:39 pm »
I have only been able to find schematics on the 35 Mhz version (JDR 3500 or Hung Chang OS-635), so I'm not sure if they are similar enough to the 20 Mhz version and it would be nice to know the parts in case something needs replacing.
Or "upgrading"? :D
 

Offline edy

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Re: My $50 scope (Hung Chang) Tenma 72-720 [Inside Photos!]
« Reply #44 on: August 10, 2013, 09:33:55 pm »
Wow, this is just hilarious yet terrifying!  :scared:

We are up to probably a dozen re-badges already....

Fortunately I bought a Hitachi 1565 at the same time, so it will be fun comparing the two.

I was hoping Dave could do a review and teardown of this Hung Chang scope. It has been a while since I heard him saying expletives (last time I think was during fake Apple charger teardown).
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Offline israel

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Re: My $50 scope (Hung Chang) Tenma 72-720 [Inside Photos!]
« Reply #45 on: August 10, 2013, 09:41:48 pm »
another one to the list

Oh my God! ... the clones attack   :) :)
 

Offline edy

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Re: My $50 scope (Hung Chang) Tenma 72-720 [Inside Photos!]
« Reply #46 on: August 10, 2013, 09:48:32 pm »
Don't forget Ramsey 2200... Also seen on ebay.

So here's the list so far (let's keep it going!):   :-DD

Tenma 72-720
Elenco MO-1251
Hung Chang OS-620
Neotronics OS-620
JDR Model 2000
A-1 Electronics
AW Sperry 620C
Tenma 72-320
Dick Smith Q-1240
Aron BS-601
Degem System 112
Ramsey Model 2200

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Offline Stonent

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Re: My $50 scope (Hung Chang) Tenma 72-720 [Inside Photos!]
« Reply #47 on: August 11, 2013, 12:49:08 am »
Don't forget Ramsey 2200... Also seen on ebay.

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Offline edy

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Re: My $50 scope (Hung Chang) Tenma 72-720 [Inside Photos!]
« Reply #48 on: August 11, 2013, 02:54:15 am »
You know, although it may be one of the cheapest scopes around, it may also be one of the easiest to service because the parts seem to be all standard off-the-shelf parts. Yes? No? Or am I just making excuses.  :-/O
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Offline Stonent

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Re: My $50 scope (Hung Chang) Tenma 72-720 [Inside Photos!]
« Reply #49 on: August 11, 2013, 03:37:44 am »
You know, although it may be one of the cheapest scopes around, it may also be one of the easiest to service because the parts seem to be all standard off-the-shelf parts. Yes? No? Or am I just making excuses.  :-/O

That's what I'm thinking at least. It's cheap but fixable.
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