Tag Archives: great

Altec 1592B repair, 1588B module, XLR pinout output etc

Recently i got a nice Altec 1592B mixer.

Each input requires a dedicated preamp/transformer module, for microphones there’s preamp, 1588B or preamp+12v phantom power, model 1588C.

I had to do a massive recapping job on the 1592B- the original caps values were all over the place-and i mean not only electrolytics-the only ones that were still measuring ok were the tropical fish and some of the lower values disc caps- though most of the electrolytics were good quality, Mallory or West Germany made, ROE (Roederstein). I replaced them all with Elnas (they seem to be the standard nowadays).

Also, the resistor after power transformer 7818 (that feeds part of the tone section, so if you have an unit that powers up but does not produce a sound, check for +18v at pin 6 of the tone board, that is linked to the power board after (out) the aforementioned 7818) was burned-clear sign that some damage had taken place. The schematic calls for a 10 Ohms resistor-i decided to put a 100 ohms substitute, much better.

Sounding good, i decided to recap also the 1588B module i have here (more are on the way, and when factory new, they were fitted with 3 modules).

After using a small screwdriver to pry the enclosure open, i took a look at this interesting blog (check it) for the schematic-i also took the time to sub the carbon comp resistors with metal film and yes-noise went down.

For your reference, here’s the resistors network:

Q1 and Q2 pinout:

Troubleshooting:

If the preamp is not working, check carefully the resistors-they break easily. One immaculate looking (inside and out, the spongy filler still in good soft condition, no leakages on the plastic screen etc) 1588B i have had a resistor broken at its base, and since the components are so squeezed together it was impossible to see it-i decided to test the transistors (thats why i took the q1 and q2 pics above) since everything was looking proper-and there-i spotted the broken resistor! The preamp would still burst in noise if i knocked the mic gently on the capsule, yet it wont amplify it properly. Thats the resistor connected to ground on the white wire-a pain to desolder too.

If you must desolder stuff, be patient-these boards wont take a 300 degrees hot iron-the circuit tracks will lift if you heat them up too much-use care.

Since someone over at the Tape Operator forum has raised the warning that the power supply may have been ill designed, i am powering it using an external psu (using the battery option), 24v dc.

Terminal: from left, my battery (external psu) connections (- and +) and pinout to wire an XLR balanced jack to the output: hot, cold and ground… in the mess between high and low impedance i went with, 600 ohms, good for any mixer or recorder input. PLEASE note 2 and 3 terminals are bridged (connected) at the terminal post. The signal is nice and strong.

I will not mod this unit, i like it as it is. Nice and retro sounding.

Roland CR8000 buttons repair made easy

Roland Compurhythm drum machine CR8000 with faulty or worn buttons.

Sounds a lot like the TR808, but a design fault makes these buttons useless after a while.

You will have to pull the plastic covers first, to reveal the spring and rubber dome under which we will drop a bit of conductive paint..

To pull the plastic part you need to push the sides using a screwdriver or two like on this video:

Youtuber The Imp Of The Perverse has made a few vids of his restoration-he used my method too, check them

Akai S900 disk drive replacement

Since keeping it strictly old school is a must, i decided NOT to go the Gotek/ HxC floppy drive emulation route to make up for my S900’s broken floppy disk drive.

Which disk drives can be used to replace the Akai S900 floppy drive? Theres a page on gearsluts with a few suggestions, but i felt the info was a bit messy and not really clear (a few yes this works, some no-nos etc).

I took an old amiga 500 external floppy disk drive and yes it works on the akai S900-just be careful about the header’s orientation. It is a drop in replacement. It can format and use modern HD floppy disks too.

So in a nutshell: amiga 500 floppy disk drives can work as a replacement for the Akai S900 sampler.

Just a piece of info from Masu.

Hohner Basset

When i bought it it looked like this


I opened it up to clean it and realised this wasnt its original colour.


It really was taupe gray before, but the years had the plastic chassis yellowing

I decided to restore it to its original colour (or as close as i could…)

After 5 months of great fun, I had to open it up because the output went silent.

Gutshots of the Hohner Basset!

Lets start with the DIN jack that connects it to the bass amp..


Keyboard:

Circuit board and caps jungle:

Inside the white enclosure there’s a lamp and a ldr.. this assembly is the actual “percussion” section.

You press a note on the keyboard, the light goes off slowly (sustain) according to the knob position, when not in auto mode.

Video below..

Pcb: 3.1967!!

Ahem this means the caps have been doing their job for 50 long years! Only one of the capacitors has failed, please note- the blue valvo 100uF cap now measures 1uF!

Output DIN and 3 pronged jack, fuse

Video showing the lamp going off when a note is keyed.

Selmer Buzz Tone

Syd Barrett’s hairy boost.. VERY WARM AND THICK. Perfect counterpart to Syd’s favourite amp settings, basically treble at 10. 

Perfunctory build on eyelet board, with external vero for transistor testing, using 2N2613 as per original.

Very surprised by the final tone, i really like it.. Sounds very nice.   
I broke out the wem copicat to have a better idea if it nails syd’s tone.

Check it out clicking here

I also made a quick little excuse for a tune to test it further.. sorry for the hurried and far from great mix:

Melanie Wright-a Buzz-Tone tryout