More product teardowns

[Alex]

To return tekfan's favour for doing a review of the Bruel & Kjaer 2305 recorder and continue his contribution, here is a list of products I would happily dissect:

Fluke 123 scopemeter
Fluke 289 DMM (upon enough demand)
TTi Ex354 Dual Power Supply
TTi TG550 function generator
Ersa I -CON 2 (with serial port) soldering station
Peak Atlas ESR60 ESR meter and Atlas DCA55 semiconductor analyser
Tektronix 2225 dual channel analog oscilloscope

[Ernie Milko]

Definitely a yes please for the Peak kit.
From what I've seen of it, it looks a bit mickey-mouse.

[Alex]

Teardown of Peak Atlas ESR60 ESR meter and Atlas DCA55 semiconductor analyser

Hard case the instruments come in. This is purchased separately.



The case has a foam insert with cutouts for two instruments, their leads and a spare 12V battery which is a great idea. Unfortunately no provision was made for the third instrument Peak makes in this category (the Peak SCR analyser) although there is space. A small pocket could be there to hold the user manuals. Overall a robust storage case.



The ESR60 measuring a 1uF MKT and a 100nF MLC capacitors.



Detail of the probes. They are gold-plated crocodile clips. There is no grommet on the case but the cables and entry point are very robust. Standard pozidriv screws, no metal thread inserts. However, the long screw length combined with coarse threads make a very robust and long-lasting mechanical joint between the enclosure pieces.



Top cover off. Notice the programming header on the left (Microchip ICSP) and the 12V battery in-PCB mounting on the right. 3 plastic feet press the battery towards the back. A standard Hitachi HD44780 compatible 2x16 LCD is used in I believe 4-wire parallel mode. The LCD is supported only by the connector, no double sided foam was used on its back.



View of the back of the PCB. On the left are the power supply electronics around a NI LDO. In the middle is the power mosfet in SOIC8 and power resistors. This is used to discharge capacitors before measurements. At the bottom a huge bi-directional zener diode connected directly across the capacitor measurement leads for over voltage protection. Notice that two wires were used for each croc clip for reduced resistance and increased reliability. On the top a PIC16F clocked externally with at 4MHz. Top right are two quad TI TLV2624 op-amps. Bottom right two Maxim MAX4614 quad analogue switches and two NAiS signal relays for routing the capacitor to the measurement and discharge circuit. These realys are very loud for their size.



Detail of the above




Over to the Atlas DCA55 semiconductor analyser. Here it is analysing an MPSA92 transistor. One complain is about the quality of the test clips. Their low cost is clear, but the real issue is with the hook of the tip which, when testing large transistors, can be bent under the force of the spring in the test clip. As a customer I would be happy to pay the extra £2-3 for a higher quality hook clips - even for infrequent use. They can however be desoldered and replaced with higher quality ones.



Top cover off, you can immediately realise Peak's business model. The units are nearly identical. Interestingly this PCB carries the name of Jez Siddons who (according to a forum) designed the ESR60. His name does not appear on the other board though.



On the back a PIC16F can be seen again, it is exactly the same as the ESR60, but lacks the external crystal oscillator as this meter doesnt require such high timing precision. On the right of the MCU are two 8-channel analogue multiplexers of the 74HC family. On the left is an LM324 quad op-amp. The input connections lack any form of protection.



And finally here are the two boards side by side.

[Kiriakos-GR]

Nice Work Alex ...

Great pictures and text .

I just wish, that the time that you had use so to make the tear-down,
to no be stolen from the hours of your studies . 

Regards.

 

[Alex]

Compares fairly with custom DMM stands...or watching the wedding.

That's our breed, super efficient to find time for the things we truly find pleasure in doing.

[Fraser]

Great teardown. Thanks

I have seen several ATLAS ESR meters on e*ay sold as 'untested' and from the later buyer feedback it is apparent that the units have suffered fatal damage to the PIC and are total scrap. The input protection may not be adequate in all cases.

[Alex]

In the manual it clearly states that the unit must not be used on powered equipment (it can be used in-circuit) or with charged capacitors. This is all common sense and there is a discharge facility on board but no details on that is provided.

The MCU is sitting behind analogue switches and op-amps, you really need to make an effort to pop the MCU. Also, the input traces have generous clearance around them which shows the input section was designed to take a high voltage pulse, or at least that was the intention. But apart from the zener diode there are no other components that can absorb a lot of energy.

[tekfan]

Nice teardown.

I would love to see the insides of a good quality soldering station like the Ersa and the Tek 2225.
I always get a kick looking at analog scopes.

[Ernie Milko]

Nice work.
They would have been better in a larger, squarer, project box. This would have added to the robustness factor. They look very flimsy.
They seem to have gone for miniaturisation, coupled with visual appeal. It's a bit like they were designed by Clive Sinclair!

I think I'll stick with my Bob Parker ESR meter and Marconi LCR bridge.

[Fraser]

Alex,

As you suggest, it would take some effort to kill the MCU and I was surprised to hear that this had occurred in view of other components being in the signal path. Maybe the e*ay buyers assumed MCU failure. As I have yet to get my paws on a dead unit I cannot be sure what dies in an overvoltage situation.

It is very hard to protect equipment from all eventualities as someone will aways find a way to stuff a unit  

I had a laptop in for repair that had been 'tested' for EMI susceptability by extending a gas cookers electronic ignition HT output to the vicinity of the motherboard and probes created a spark gap....a stray flashover to the laptop PCB ended it's life there and then    It was beyond my abilities to revive it and considering the stupidity of the owner, he deserved to be hit with te cost of a new laptop.

[Alex]

ERSA I-CON 2 with Serial Port Teardown

This is Ersa's flagship hand-soldring station, considered one of the top manufacturers of soldering solutions. This particular one can accept two soldering tools and features a 'serial port' to connect to control a fume extractor or an IR heatingplate. I would love to explore the rest of these components, but the 'serial port' version only comes with the i-tool (the soldering pencil iron). My expectations are high, you had better got this right Ersa!

First off, a view of the station I will be taking apart (after turning on):



Splash screen. The illuminated ON/OFF switch is at the front together with two DIN 45326-type connectors for the tools. There is a banana plug for an esd mat in the centre. The user-interface input is the rotary encoder/pushbutton at the top right. Very practical as the station has many options in the form of a menu list. It looks a bit 'off' without a marking saying 'Menu' or 'Set', that would be a nice addition. The front is from aluminium but unfortunately it is just adhered to the case. Under heavy use at elevated temperatures the sharp corners at the bottom might become detached.



Bottom view. Rubber feet, vent cutouts and 4 torx screws. Very robust.



Back side. IEC connector with built-in fuse and space for a spare one. Excellent. Above that is the 'serial port'. A huge sticker warns this is not an RS232 standard port, yet they insist on calling it RS232 on the board and documentation. Again no marking which gives the impression it was an afterthought or a marketing experiment.



Before the main event, lets have a look at the soldering iron and stand. The i-tool is very small and ergonomic. It has a silicone anti-slip surface (grey) and can deliver 150W. What doesnt make sense to me is that the station is rated at 120W and so is the internal transformer. Maybe the transformer is momentarily overloaded (the data plate should still say 150W) but what is clear is that you cannot be using both tools at the same time (the menu wont let you anyway). Despite the large power the handle doesnt get too hot. The stand is from solid high temp rubber. Big thumbs up for doing this as it can be put under hot water and brushed to clear all the solder blobs. The base has 6 holes where, I believe, you are supposed to mount soldering tips as shown. It works great. However I only received 4 pillars (as shown), I could not find any as spare parts, and they are not mentioned in the user manual. The soft abrasive pad comes as standard.



Here is the soldering pencil taken apart. Tip, retainer assembly, heating element and main body. The heating element/tips are very small hence very reactive to temp changes. Inside the main body there is a sensor assembly (not reed switch) to detect when the tool is about to be used.



Detail of the heating element. Robust sealed construction with gold-plated contacts.



The connecting cable is insulated with high temp silicone, and I will prove it to you!



Cover off. I am pleased to see the space is actually used and there are no lead slugs for weight. Instead, a linear power supply adds the majority of the weight. This is great as, combined with the feet, it wont go anywhere on the bench. Centre(almost) tap on the transformer, the 24V winding is for the heater and the tap is for the control electronics. High temp fibreglass sleeving and connectors for almost all cabling inside the unit.







Detail from the front connectors area. Insulated blade terminals and a true ON/OFF switch. Those things on the trafo are not rust, but some sort of cardboard remains? probably from the part's packaging. The earthing banana socket is soldered well (although it would not meet IPC standards). It does however lack a sleeve, possible a heatshrink piece which would add some mechanical support.



The banana socket is soft-grounded via a 220k resistor, while the soldering tip is hard grouned. I was surprised to see a PCB pin was used and not at least a blade terminal. An in-line resistor from the banana to the IEC connector would have been more reliable. I belive Tektronix had an issue with PCB-based grounding on the TDS220 DSOs and had to do a recall.



I will post up to here to save it.

[Alex]

Part 2

Here is the control electonics. 3 assemblies: LCD, main board and 'RS232' board.



Detail of the heater power section. Optocouplers were used in combination with SanRex Triacs to power the heaters. No high power rectifiers were used, the heaters are fed with AC.



Detail of current sense shunt resistors. On the right you can see the diodes and rectification circuits for these signals.



Detail of the MCUs. Two ATMEGA AVRs clocked at 16MHz and logic buffers, I belive for the LCD. Power supply on the left, PCB fuse on top. The function of the smaller MCU is not clear, at I guess I would say it is responsible for the devices connected to the serial port.



LCD assembly. Is uses LED backlight.



Finally, detail of the 'RS232' board. All signals are isolated using an optocoupler, an integrated transformer isolator (ADUM1401) and a relay (other side)! On the other side there is also a MAX3226 - a feature rich high speed version of the MAX232. What is odd is that the buzzer (used to indicate that the tip temperature is within a preset window) is placed on the 'RS232' board when I know the non-RS232 versions also have a buzzer. Most likely the smaller AVR on the main board took up the space originally intended for the buzzer. Anyone with an ICON2, non serial port version we would like to see your main board! ;-)



Lets see how quickly I can put everything back together -no leftover screws-. All this soldering station talk made me want to solder; like watching cookery shows makes you hungry.

Alex

[tekfan]

Wow! That's quality construction right there. Very interesting shunts on the main board. I still can't believe that small heating elememt can supply 150 watts of heat. Amazing!

[zaoka]

What I noticed with Ersa is that its tips are very good, somehow its easy to solder with. Its been long time ago but I remember all technicians prefered Ersa over Weller.