Crawls Backward (When Alarmed)

IconProjects, musings about guitar builds, guitar repairs, vintage tube amplifiers, old radios, travel, home renovation, and other stuff.

Hacker RP-38A Recapping and Light Restoration

Oddly enough, when I started the blog way back when, one of the main topics I thought I'd be writing about was restoring radios.  But then I got sidetracked into building amps, guitars and who knows what else.  So ironically, this is the first post involving an actual radio being worked on I think.

I mentioned my Hacker RP-38A "Hunter" radio in an earlier blog post. It's a great English radio from about 1969-70 or so.  It has Long Wave, Medium Wave (aka the AM Broadcast band here in the US), and an FM band (up to 103 MHz).   The radio has a fairly large oval (about 5x7 inches) speaker, separate bass and treble controls, and a push-pull transistor output stage.

Yes, I know, imagine ME playing with transistors. 

Not to digress too far, but I have an affinity for many things English.  Blame it on the usual suspects: four Liverpudlian musicians, sports cars made in Abingdon-on-Thames, Berkshire (now Oxfordshire), etc, etc.  So when I saw some Hackers on you-know-where auction site, I had to have one.  Which became...six? seven?  eight?  I need to count them all.

Turns out Hacker was the finest English-made consumer radio in its day.  The build quality is first rate, and the reception and tone quality is on par with the more famous German makes.  And in classic English fashion, there is a nice familiar, warm, personal quality about them.  It's hard for me to put into words, but it's the same reason I'd rather push an MG than drive a BMW. 

Anyway, back to my beloved Hacker Hunter.  I've had it for about 3 or 4 years, and it has run perfectly with no issues.  The treble control didn't seem to do much, and I had to roll off the bass to get a tone I liked, but it sounded fantastic, especially on classical music.  But a couple of months ago, all at once it developed a bad hum - which sounded to me like a filter capacitor had finally gone belly up.  Not surprising considering the original caps were about 30 years old.

After putting it off for a while, I got a chance to open up the radio and take a look.

Here's a shot from the back with the back cover removed.  The radio runs on 18 volts DC (as do most Hackers).  The 18 volts comes from 2 PP9 batteries wired in series.  The PP9, to my knowledge, was never sold in the US, and it's virtually extinct in the UK as well. 

In order to get the radio running, I rigged up 2 battery holders, each containing 6 C cells.  Each one adds up to 9 volts...18 volts in series.  The radio doesn't have a huge current draw (about 20 ma or so), so 12 C cells last a long long time - over 2 years so far, with the radio being used an hour or so a day on average! 

This is a closer shot of how I rigged up the batteries. 

I didn't want to cut or modify the original battery clips, so I wired alligator clips to my new battery holders, and then clipped them to the appropriate terminals.

The downside is that 12 C cells adds a fair bit of weight to the radio.  On hindsight, I probably should just use 2 modern 9V cells (PP3); I will do that when this set of batteries dies.   At this rate, that should be another 2 years!


Post a Comment 0 comments:

Post a Comment