Harrison 2824c Restoration

Since there is great threads of restoring the 32-series Harrisons, I thought of starting a little pictorial of the restoring of my 24-series which is pretty much the same desk than 32´s but with 3-band EQ and only 4 auxes on every in/out channel and no lo-pass filters, just hi-passes. It´s the "lighter" version of it. (but still 300 kg!!!) Maybe this might be helpfull for somebody with similar project. I´m adding more photos along the way.

Mine is 2824c dating from ´81, one of the last ones made. It´s with Valley People/Allison EGC-101 VCA´s and they do sound really smooth.
We´re starting from PSU recap and we´ve already made loads of cleaning and now only 1 channel is dead and couple of other just need extra cleaning. After that it´s re-capping everything else.

The PSU

BIG caps!

The small Sprague caps in the PSU.

In/out channels

In very nice shape, lucky guy, well i've seen some other mixers looking for restoration, and they were far away from this one, but maybe those pictures are after the worst looking ones...
Anyway very nice.

Yes, now it looks much better. When we started it looked quite sad because it had spent 10 year in an non-heated attic of an wooden house in Finland... But these consoles were literally built like tanks, so after one day of cleaning like maniacs, this was the result. But there´s still LOT to do, pots, chips, caps, switches even... but the sound is already now very impressive. And to my experience, the recap is going to make a big difference.

Nice to see another Harrison alive and well in Finland Have EGC-101's in my older console too and they do sound good!

Martin

Hello Martin!

Nice to see you here! My console was actually originally owned by Finnish Broadcasting Company and so it has been here since ´81. You have TWO Harrisons if I have understood correctly?!

What about those caps, did you use the original values like 100uf/25 or did you increase them? And did you change the Ha-4605 chips? Or what about 74c74 or 74c151 etc? Today we recapped the Quad Master and the result was great: more detail and punch. The old ones were really shot. I used Panasonic FC LE´s. Here´s a pic of the pre-recap Quad Master.

And the In/Out strip...

And this is the Valley People EGC-101 VCA. Sweet...

telefunk said:

You have TWO Harrisons if I have understood correctly?!

Click to expand...

Yep, a 3232AB from Sweden and a 4832C from California.

telefunk said:

What about those caps, did you use the original values like 100uf/25 or did you increase them? And did you change the Ha-4605 chips?

Click to expand...

Have recapped both consoles but kept the original values. As for the op-amps, we've done a lot of listening and testing, and so far my favorite is stilll 5532s with current sources to run them hotter (built special adapters with SMD), tested this in a module with Bruce Swedien and he loved the sound too. Silky, warm and punchy. But needs a HEAVY power supply...

Also tried a mod where I bypassed the two patch points by rewiring the FET card. Using tape return for inserts anyway.

telefunk said:

Or what about 74c74 or 74c151 etc?

Click to expand...

The 151's are on the FET card, right? They pop easily because of the voltage rating. Have replaced mine with another one, can't remember the number now.

Martin

Martin B. Kantola said:

As for the op-amps, we've done a lot of listening and testing, and so far my favorite is stilll 5532s with current sources to run them hotter (built special adapters with SMD), tested this in a module with Bruce Swedien and he loved the sound too.
Martin

Click to expand...

Martin, what means "run them hotter"? Did you bias them into Class A with a current source instead of the usual resistor or did you do something completely different. If so what exactly?
cheers

jensenmann said:

Did you bias them into Class A with a current source instead of the usual resistor

Click to expand...

Yes.

Martin B. Kantola said:

telefunk said:

You have TWO Harrisons if I have understood correctly?!

Click to expand...

Yep, a 3232AB from Sweden and a 4832C from California.

telefunk said:

What about those caps, did you use the original values like 100uf/25 or did you increase them? And did you change the Ha-4605 chips?

Click to expand...

Have recapped both consoles but kept the original values. As for the op-amps, we've done a lot of listening and testing, and so far my favorite is stilll 5532s with current sources to run them hotter (built special adapters with SMD), tested this in a module with Bruce Swedien and he loved the sound too. Silky, warm and punchy. But needs a HEAVY power supply...

Also tried a mod where I bypassed the two patch points by rewiring the FET card. Using tape return for inserts anyway.

telefunk said:

Or what about 74c74 or 74c151 etc?

Click to expand...

The 151's are on the FET card, right? They pop easily because of the voltage rating. Have replaced mine with another one, can't remember the number now.

Martin

Click to expand...

The FET card has 157´s but mine has been replaced with CD40257, seem to work great. The 151´s are in the mute bus with 74c74´s and i had TEN of them broken, so it must be the voltage rating i guess. But the 151 HAS to be the 74c151, not for example 74hc151 because 74hc151 has voltage rating only up until 5v and mute bus works at 7.5v.

We changed the caps to few input channels and the master channels already and i have to say that the change was surprisingly big. I guess the old caps were really dried out.

In my 2824 last two meters in the meter bridge are marked A and B. I cant seems to find what they are, Am I missing something? ;-) 

Martin:

For the replacement of the HA 4605-5, how did you like LM837 vs. MC33079? If i´ve understood correctly those are direct replacement for the old ones. And how about AD797 for the mic pre? Also a direct replacement I assume?

When upgrading "summing bus" op amps, are we talking about the op amps in the Group master line drivers?

Tried these quads:

LT1125
LM837
OPA4228
TLE2144
LME49740
TLE2074

The 5532 circuit described above still was the best one to my ears. Haven't played with the mic pre's yet, have both xformer and electronic versions in the older console (16 each).

Martin

Working on the quad/group masters and monitor channels. LOTS of caps. At last figured the A and B meters: they are the echo aux meters. I got rid of all the problems with molex-connectors by taking the corrosion out and finding all the broken solder points under the FET card in the main board. Huge improvement!

This is the monitor channel pre-recap...

Ok, here´s a few pics from the re-cap sessions...now it´s all done, more than 1200 electrolytics changed...but it was definitely worth it. Sound is more defined and low end is bigger and more reflective and hi-end has more detail. We changed all the 100uf caps to 220uf and all 10uf´s to 22. And the VCA-input tantalums were changed to 22uf electrolytic, much better choice. The eq´s will get MC33079´s and HA-4605-5 will be changed mostly to LM837. And mic pre amps will get AD797´s in place of HA 911 (3500). The PSU caps were kept about the same values except the big ones were increased to 47000uf´s and to 15000uf´s.

The biggest issue was actually the molex pins in the mainboards for the FET cards, there was some corrosion that had broken the solderings. I´ve read someplace that changing the molex pins to gold plated ones you will get rid of all the problems but re-soldering should be enough!

Very satisfying project.

And this is the pile of strips without caps...