Bob Parker's Blue ESR Meter Assembly & Comments

[Bob Parker]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

I'm glad there are so many experts on how the circuit works. I'll just sit back and read all the comments - saves me the time of writing.

[Krankshaft]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Here is a great description on how the circuit works and a schematic:



Your problem is probably in the LED display multiplexing circuit.

Check around Q13 for both correct transistor polarity and the proper value resistors in circuit. Both Q13 and Q12 are responsible for connecting all of the common cathodes on their respective display to ground.

When it's time to addresses display 1 Q12 conducts and IC3 then sends current to the proper segment anodes they then illuminate.

After it's done Q12 shuts off and Q13 comes on IC3 again sends current to the segment anodes. I believe this is how this circuit works. Someone correct me if I'm wrong.

This is done faster than the eye can see so it appears all segments on both displays are lit at once. This allows you to drive two displays with the same 7 segment anode lines and most importantly a single display driver IC.

Q13 is responsible for the second display. Without it the segments on that display can't illuminate even though they are being driven by IC3 on their anodes.

Hopefully the reason it's displaying 0 is because you're shorting the probes because it's supposed to display a - on the left display when they are apart.

[Toasty]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Your pictures are of...
Leads shorted together?
Leads not shorted?

Swap the displays, verify operation of other.
Decimal point LED in correctly? Does it even flash when leads are shorted?
Do you get the ( - ) sign in left display without leads shorted?

Toast

[Agent24]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Stupid message board. I wrote out a detailed description of what to check, and then it wouldn't let me make an edit so I've lost it all.

OK, to summarise.... please resolder Q12's (2N3904) leads and R27's (4.7K) leads. All the solder joints should be smooth and shiny, and those connections in particular don't look like that in the photo.

Good luck.

I thought that it would be Q13 that would be in question? Maybe I don't understand how the circuit works...

Can you tell me why you would check Q12 in this case?

[Krankshaft]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

I'd say whiskers are more of a problem with lead free solder.

Even manufacturers had a lot of problems with whiskers when the lead free ROHS craze started. Surface mount IC pin spacing doesn't leave much room for errors.

[Bob Parker]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Thanks Bob i will do that and let you know how it goes! Sorry about the message board screwing up on you, now im curious to what you had to say! Always open to learning about this. Ill let you all know soon.

Thanks

Howdy again.

I'm so buried in emails right now, that I don't exactly remember what I wrote in detail.

For your info, it's exceptionally rare to encounter a defective transistor. You're about as likely to win the lottery as find one.

The big killers of the ESR meter kits are (1) Soldering defects especially dry joints and to a lesser extent solder whiskers/bridges, and (2) Components in the wrong place. You would not believe how many people put the 220 ohm and 220K ohm resistors in the reversed places.

Your phone photos are pretty good. Good enough to easily see all the component values and the general condition of the underside of the board. Thanks but for now I don't think I need photos any better than that.

Also for your info, I've attached a photo of the back of a Blue meter board to show how the solder joints should look. I hope all this is of some kind of help.

[bedford_repairs]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Stupid message board. I wrote out a detailed description of what to check, and then it wouldn't let me make an edit so I've lost it all.

OK, to summarise.... please resolder Q12's (2N3904) leads and R27's (4.7K) leads. All the solder joints should be smooth and shiny, and those connections in particular don't look like that in the photo.

Good luck.

Thanks Bob i will do that and let you know how it goes! Sorry about the message board screwing up on you, now im curious to what you had to say! Always open to learning about this. Ill let you all know soon.

Thanks

[bedford_repairs]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

I appreciate the quick responses.

Agent 24:
Thank you for the information. I did first check continuity on the Q13 transistor and all checks out. I then removed it and checked the transistor to test it w my multimeter, guess this is where im a bit green. I know the transistor is a NPN and i looked up the data sheet and see pin 1 is the Collector, pin 2 is the Base and pin 3 the Emitter. So my question is what reading should i see on the meter as this is a switching transistor to verify if it is working properly?

Mr. Parker they came from my phone so i hope they show enough detail. If there is anything else you need information on or pictures of i will gladly post them ASAP.

Thank You both again for your time.

[Bob Parker]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Ive purchased the meter and after i finished assembly and im having an issue with the right side LED and Display lighting up.

I looked over a few posts for trouble shooting and the only thing i could come up with is IC3 may have been bad but i since replaced the IC and i am getting the same results.

Any ideas?? Here are some pictures of the front, back and the display.

Any input would be greatly appreciated.

Stupid message board. I wrote out a detailed description of what to check, and then it wouldn't let me make an edit so I've lost it all.

OK, to summarise.... please resolder Q12's (2N3904) leads and R27's (4.7K) leads. All the solder joints should be smooth and shiny, and those connections in particular don't look like that in the photo.

Good luck.

[Bob Parker]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Thanks for the detailed photos. I'll have a careful look at them and see if I can see what's causing this problem, and get back to you.

[Agent24]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

If the 4094 was OK, I would check transistor Q13 which switches DISP2 and LED2.

[bedford_repairs]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Ive purchased the meter and after i finished assembly and im having an issue with the right side LED and Display lighting up.

I looked over a few posts for trouble shooting and the only thing i could come up with is IC3 may have been bad but i since replaced the IC and i am getting the same results.

Any ideas?? Here are some pictures of the front, back and the display.

Any input would be greatly appreciated.

[Krankshaft]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

By the way, if any of you are currently getting a Bob Parker Blue ESR meter kit and also want to have the satisfaction of assembling it to the max level of "perfection"

Haha what can I say? The first kits I built were FM transmitters where you want the components as close to the board as possible. Especially in the RF circuits guess that mentality never wore off.

[Bob Parker]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Yeah, thanks for all that! I think that somehow I've missed ever seeing this thread before now.

[sds]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Thank you for Imformation.

[Huckfinn]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

By the way, if any of you are currently getting a Bob Parker Blue ESR meter kit and also want to have the satisfaction of assembling it to the max level of "perfection", use the info Krankshaft gave you and also consider adding my mod. I also used sockets for the two IC units as well as the display and the blue discrete leds that make the decimal points, but I upgraded the socket from the standard side wipe Kovar metal style to machined contact gold plated style for reliability. The two brands that work well are the old Augat [might still be available or no] and the current Mill-Max brand. I just bought single long socket strips that can be cut [broken with care] to the right length from the strip, one row at a time. And since winter is coming up, [USA] it might be a good idea to get and use a grounded anti-static mat and wrist strap when handling the IC units and the displays. A 3M mat works well, and so does the one Radio Shack sells.

Huck

[Krankshaft]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

That meter may not have autoranging and that's a major negative for me.

Next to the testing socket it's labeled 1, 10, and 100 I think those are measuring ranges for ESR.

[PlainBill]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

I am thinking of buying one of these kits myself, would you recommend it?

To me, it's a toss up. I have one of these meters, and it does it's job quite well. But I've been looking fondly at the ESR 3.1 Micro in this thread.

PlainBill

[Krankshaft]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

Holy ancient post Batman!!!

Yes I would it's saved my ass more than once sniffing out tons of bad caps in TVs. Including 85C Rubycon's that looks completely fine.

If you're serious about servicing and you want to save time it's a must.

[Agent24]

Re: Bob Parker's Blue ESR Meter Assembly & Comments

I am thinking of buying one of these kits myself, would you recommend it?