Monthly Archives: July 2016

Another stereo.

Recently was offered this hi-fi by a work colleague. Garage clear-out, it had been sat in there for years.

Marantz MR1155

It’s a Marantz MR1155, from the early malaise years of cost-cutting and design setbacks. It also didn’t work. Power was applied before I got it, and apparently it went click and made a bit of a crackle.
Sure enough, it would power up and come out of protect, but not much else happened. Evidently the protect circuit was not detecting a particular problem so that was kinda okayish.

dust werewolves

With the lid removed, the contents of the device appeared to be mostly lint. Yuk. That has to be the worst hifi I’ve owned yet in terms of dirt.

clean

Thankfully it all cleaned up nicely.

stripped down faceplate

Pulled the front off after work, removed all the buttons (they had gone green and fusty) and brought it all home to clean up. Judicious application of drill and polishing mop got it looking respectable again.

shiny

Not perfect by any means but definitely better.

lid

Cleaned up and put the lid back on. Fairly respectable.

in bits again

Brought it all home and started to poke about. Pulled up the manual off HifiEngine and set about looking for the cause of no audio. Powered it up, the main amp voltages were pretty much in spec, but the FM/AM/Phono/Preamp board was dead, with hardly any voltage. Bypassed the preamp board and fed the power amp board directly- presto, greeted with slightly clipped but definitely OK audio. The expensive amplifier modules are still OK.

caps

Ordered the full replacement of electrolytic caps to shotgun all the boards. Over the course of a couple days I replaced everything. Still no voltages, so I replaced the transistors that control the voltage and protect circuit.. nothing much. Further troubleshooting found the 14V Zener to be almost a dead short over 0.3V so I went to desolder it and it cracked into 2 pieces. With it removed, bringing up the variac got the voltages to rise. There’s the problem then. Ordered a couple 14V Zeners and whilst in town stopped at Radio Shack and picked up a couple 12V ones to see if that would get it to come to life:

alive!

Sure enough. Not very good but operational. Went to tune the FM because it was not working very well at all post e-cap replacement. Broke the discriminator tuning slug (even using a fiberglass tool of the correct size) so pulled that out and took it to bits. Ordered a couple replacement cores, so need to wait until it’s all back together before readjusting.

10.7MHz transformer

Go figure. It had to break..

Reflective! Also, frosty.

Bought a mirror from a gentleman in Canada.

mirror

Bottom one (old) being held up. Sunshine and humidity made all the silver fall off. The new one looks new by comparison.

Also moved the car and mowed because the grass is growing fast this season.

grass

That’s 4 days’ worth of grass growing around here.

frozen

Also the new heater element arrived for the freezer. Not a day too soon, it was beginning to freeze up. That again was 4 days’ of ice.