Simpson 260 Series Analog Meter

One problem with analog meters not used for some time, is battery leakage on the circuitry. Such was the case with the Simpson 260 in the SFC lab. Upon opening the case and visually inspecting the damage, I noticed that the breaker circuit was corroded. Possibly causing the breaker to trip every time the meter was used.




I dissembled the breaker circuit from the main board, and cleaned off any battery acid that leaked onto the board using contact cleaner and a scraping tool. After I had cleaned the breaker circuit, I noticed that a diode was corroded. Taking the diode out of the circuit, and testing it yielded it to be faulty, and need of replacement.





After replacing the corroded diode, and everything placed back together, the meter was then tested to see if it was still operational. As was suspected, the damaged diode from the leaky battery was the issue.



For testing the Simpson 260, I placed a digital meter in parallel of it while connected to a DC power source. To make the Simpson read more exact, the pointer adjustment was used to set the needle to match the Digital DC voltage. This was not a major change in tuning, but was needed after handing the Simpson 260.
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Simpson 260 Manual

Simpson 260 Schematic

Preventative Maintenance

As a part of the Biomedical Engineering Technician program at SFC, we perform preventative maintenance checks on medical equipment that a BMET could encounter in the field. Preventative maintenance involves safety checks using the medTester 5000, the medSim 300, cleaning filters, dust from circuitry, and testing safety alarms. Below you will find some of the equipment we work on:

Puritan Bennet 7220 Ventilator

Hewlett Packard Monitor and Model 64

Student Lab Station

If you click on the photo you will see two function generators, two oscilloscopes, and one DC power supply. Also, analog and digital meters, with the decade resistor boxes under the computer monitor.

FreePulse Wireless Headphone

These were given as a gift by a good friend. After about four months of use, the headphones themselves would not charge correctly. The charge light on the connector would blink once after plugging into the power adapter. Upon contacting Logitech for instructions on how to open and diagnose the problem (perhaps a loose wire), I received the following email from their tech support:

Sent Email to Logitech:
A friend gave me a pair of logitech pulse headphones - f-0461A
I'm having trouble repairing the power port on the headset. When I plug in the charging wire, the orange light blinks for less than a second, and goes off. I believe there may be an open some where, but can't get the darn things open. I've gotten one screw out. Does the side pop off, or is there another hidden screw somewhere?
Thank you!

RESPONSE:
Dear O,
Thank you for your e-mail
I understnad you are trying to open your headset to repair it. Unfortunately for safety reason I cannot give you any information regarding the dismateling or repair of any of our products.

Please do not hesitate to contact us again should you have any further questions or comments regarding our products or procedures.

Kind regards,

****************
Logitech Europe SA
Customer Support.

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In Logittech's defense, giving instructions on repairs probably violates a company policy, and his response is understandable. However, on their website is the instruction manual for the FreePulse Wireless Headphones . Within are instructions for opening the headphones and wireless adapter to replace the Li Ion battery packs.

I opened the headphones, and found nothing wrong with the wiring. What I did find, was that the Li Ion battery pack to be the problem. When I disconnected the battery and allowed it to sit for five hours, plugging it back into the headsets seemed to fix the "no charge" problem.

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A second issue with the Logitech FreePulse Wireless Headphones, was the adapter. The sound level would drop to almost half.

The cause for the sound dropping to half power, was a grounding issue. Apparently the grounding wire was not making contact with the output pin.

To fix the ground wire, the device had to be connected to a CD player. The open in the wire was found where it connects to the shield for the output pin. To fix this, a small amount of solder was applied to the ground connection.

Leader LFG-1300s Function Generator

Problem: No AC voltage out. Device turns on, but there is very little output voltage.





Click for Service Manual


Diagnosis: Blown 200mA QUICK FUSE (Part # F401) located in the Output Modulator Stage.