Holzforma / Farmertec G395XP chainsaw – initial evaluation

I purchased a Holzforma G395 chainsaw for $410 delivered but without bar and chain. It is a Chinese clone of the now discontinued Husqvarna 395XP It is a relatively old technology carburetted engine, prior to the strato technology (stratified scavenging) of the X-TORQ etc.

The Holzforma G395 has slightly lower published power rating than Husqvarna 395XP.

Previous experience documented at Holzforma / Farmertec G372XT chainsaw – initial evaluation shaped the approach with this one. Continue reading Holzforma / Farmertec G395XP chainsaw – initial evaluation

Last update: 18th November, 2023, 9:10 AM

Rigol DM3058 firmware upgrade – post mortem

This item documents a failed attempt to perform a firmware upgrade on a Rigol DM3058.

By the book

The process attempted to upgrade the firmware from v2.02 to v2.03 using the method described by Rigol and upgrade file from their official website.

There were not power interruptions during the upgrade which hung and was shut down after an hour. I might add that I had just upgraded two other DM3058s using the same method, same USB stick.

Email was sent to Rigol Support for help, none came. No surprises there, Rigol are a Chinese company.

I have later found comments that the upgrade may fail if Rigol UltraSensor has been used on the instrument. Others comment on difficulties working with some USB sticks.

The firware is loaded into a flash (external) memory chip attached to a ADSP-BF531 processor chip.

Above, the 4MB flash memory chip branded Spansion, later to become Cypress, then Infineon. Continue reading Rigol DM3058 firmware upgrade – post mortem

Last update: 13th November, 2023, 3:12 AM

Review of Shahe torque screwdrivers ZSQ-0.6 and ZSQ-3.0

This article gives initial impressions of two budget torque screwdrivers:

  • Shahe ZSQ-0.6: 0.1-0.6Nm; and
  • Shahe ZSQ-3.0: 0.5-3.0Nm.

They were purchased on Aliexpress from the “official Shahe store” for about $33 each incl shipping. There are no brand markings on the screwdrivers.

Above, the two torque screwdrivers, plastic bodies but mostly metal internal parts. Continue reading Review of Shahe torque screwdrivers ZSQ-0.6 and ZSQ-3.0

Last update: 14th November, 2023, 6:25 AM

Simsmith model of Ruthroff 1:4 voltage balun

Ruthroff described some baluns in 1959, and which have had continuing application. This article discusses the 1:4 Voltage Balun.

Voltage Balun

From Definition: Current Balun, Voltage Balun:

An ideal voltage balun delivers voltages that are equal in magnitude and opposite in phase.

A good voltage balun will approach the ideal condition. It will deliver approximately equal voltages (wrt the input ground) with approximately opposite phase, irrespective of the load impedance (including symmetry).

Common mode voltage ((V1+V2)/2) will be small.

If the load impedance is not symmetric, then the currents flowing in each output terminal will not be equal in magnitude and opposite in phase.

An ideal voltage balun has zero common mode impedance, a good one has very low common mode impedance (ohms).

Ruthroff’s 1:4 voltage balun

Above, Fig 5 from (Ruthroff 1959). Continue reading Simsmith model of Ruthroff 1:4 voltage balun

Last update: 15th November, 2023, 5:19 AM

RF compensation of power relays – bigger relays

RF compensation of power relays referred to a video I have recently posted RF compensation of power relays.

Above, the example relay.

So, does this technique work for bigger relays?

Firstly, small is beautiful… it is easier to get good compensation of smaller relays over a wider frequency range.

Above is an example relay by K5UJ for discussion. I do not have measurement data for this relay box, but experience tells me that at HF, the compensation technique discussed above is likely to give good results for its intended purpose as a HF T/R relay. Continue reading RF compensation of power relays – bigger relays

Last update: 20th October, 2023, 7:28 AM

DSO – dead time after a trace

Oscilloscopes have always had some dead time after completing a trace when they were not able to be retriggered.

I noticed a hand held DSO that I was evaluating to produce a different result on a train of pulses that repeated every 10m, different to a budget Tek TDS2024C DSO.

So, I have conducted an experiment comparing 7 DSOs that I can put my hands on.

The test waveform is a burst of 1MHz 50% square wave of adjustable number of cycles n, and the burst repeated every 100ms.

Setting the DSO timebase to 1µs/div and NORMAL trigger, and with zero time at mid display, the initial display with n=10 is a flat line up to mid screen, then pulses (5 or 6 depending on the display width) to edge of screen. This is rewritten every 100ms with every new burst. Continue reading DSO – dead time after a trace

Last update: 24th October, 2023, 7:37 PM

Ongoing MR16 LED failures & purchasing frustrations

We have around 25 MR16 LED lamps, half of which are almost never used, the other half probably average 4 hours per day, or ~1500 hours per annum.

Remember that greens touted this ‘green technology’ to have a life of 100,000 hours. More recently, claims have been moderated to 10,000 to 25,000 hours… but that is a single LED element alone, not a set of them, and it does not include failures of the internal and external drivers. IOW it continues the fraud of green lighting.

Above, the MR16 50mm LED lamp. Continue reading Ongoing MR16 LED failures & purchasing frustrations

Last update: 12th October, 2023, 4:52 PM