Höcherl & Hackl PL506 DC Electronic Load

I bought a Höcherl & Hackl PL506 DC electronic load just recently. It’s a nice piece of equipment to test switch-mode power supplies (SMPS) or any DC power sources like solar modules or batteries. I will need few of those for Tektronix SMPS repairs. As far as I can tell, DC electronic loads are rather rare and expensive units. So I grabbed one on an auction site for a very decent price compared to current offers (which is crazy, they ask 600…1000 EUR for such unit).

Höcherl & Hackl PL506 front panel.
Höcherl & Hackl PL506 back side.

After unboxing and shaking the unit, I noticed a strange noise. Since it’s easter holidays here in Germany, I thought it was some kind of a “Kinder Surprise Egg” time!

But no, I was disappointed. No easter eggs 🙁 It was the fan which broke off.  I looked for other damaged parts and defects but there were none. No signs of burned parts, bad electrolytic capacitors etc. Looking good inside!

Höcherl & Hackl PL506.
H&H PL506 – The unit was shipped like this. The rubber vibration isolators broke and the fan fell off.

The vibration isolators probably became brittle over the years and broke during the transport. The fan fell off and had to be reattached.  The front panel buttons are a bit crusty, too and will need to see a maintenance one day. The heat sink could need a clean-up, too. Build-up of dust and dirt diminishes heat transfer and can cause either performance issues or overheating of power dissipating MOSFETs.

Rubber dampener with metal thread insert.

I was looking for a suitable replacement in my electronics parts bins but found nothing. I used zip ties to reattach the fan to the heat sink. The unit was fixed in less than 10 minutes.

Problem was fixed with zip ties.

A quick test with a random 13.8 V SMPS was successful. I was able to load 19.9 A at ~13.4 V which corresponds to ~267 W output power of the SMPS. This DC electronic load is capable of dissipating 500 W continuously or up to 900 W short-time. This was a short-time test with 4 mm banana cables since I didn’t have proper high-current cables at hand.

Höcherl & Hackl PL506. Testing a 13.9 V / 20 A power supply.

Very nice addition to the lab. Hope this will be useful for future repair and maintenance projects!