Friday, June 14, 2019

Harmon/Kardon Amp Teardown

On a string of days off I recently decided to do a bunch of spring cleaning, including tossing a ton of old parts and other crap in my garage leftover from the E36 overhaul. As I circled around the E36 I remembered that I had wanted to pull the amp out of the vehicle, bring it back to my lab, and open the unit to inspect and repair it as necessary to remedy several non-operational channels.

The top of the pcb reveals a lot of through old components. This is pretty typical 90's tech. Note the extensive use of high quality film capacitors in addition to more conventional electrolytics.

A closeup of the TDA8563Q amp modules as well as the glue used to prevent loosening of the reservoir capacitors in a high vibration environment. Unfortunately the modules were discontinued back in 2015.

The bottom of the two layer board reveals all of the active filters, implemented with surface mount parts including huge (by today's standards) 1.27mm pitch SIOC and 1206 passive components.

The good news is that I was able to pull the unit out, take it back to my bench and open it up quickly enough. The bad news is, ironically, I found the PCB and all components in good shape, at least physically. I expected to find at least a few leaky / blown electrolytic capacitors or perhaps a couple of burnt amplifier modules (TDA8563Q) but I found nothing. Nada. No obvious hints as to what could be wrong.

Of course, capacitors can and do fail without blowing their tops and silicon devices routinely self-destruct with no outward evidence, but without any physical hints as to the location of the problem that left me with exactly two options: test components randomly in or out of circuit, or start a time-consuming reverse engineering project including developing test jigs that would allow me to power the unit on the bench as required to probe the circuits looking for faults.

Given that I have no time to waste these days neither option appealed to me so I resolved to reassemble the unit, put it on the shelf for possible future experimentation, and make an effort to schedule some time later this year to install the audio components that have been sitting on my shelf for the better part of five years.

Part of the reason I have been in no rush to do this work is because I do not like the headunit I purchased some time ago. It was the lesser of the various evils available at the time, but it's still a steaming pile of garbage like every other single DIN chassis receiver on the market today. I won't rehash my issues with that unit here but you can read them here if you want.

There is a possible light at the end of the tunnel, however. It turns out Blaupunkt is reportedly releasing an updated version of the Breman SQR46 any day now (tm). The original unit shipped in Porsches many years ago but I think this unit would look right at home in the E36 as well. If that does make it over to US shores or I can acquire it on the gray market I'll sell my existing headunit, pick up the new Blaupunkt, and schedule some time to integrate it.

Video: E36 Harmon/Kardon Amplifier Teardown

Mileage: 271050