Tag Archives: pcb

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.

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Hohner Cembalet repair

My beloved Hohner Cembalet I has gone silent, all of a sudden.

Here we go with a few pics i took for reference of the main board.

They may help someone else whos trying to fix his Cembalet.. I hope.

Schem and user manual (in kraut):

Hohner Cembalet User Manual with schematic

Update: the Cembalet healed itself and now it works great. I did not have to do anything to it, it just works again, magic, bang.

A friend who’s an electronic repairer said that the most important part to watch out for is the inductor (Spule in german), as it’s custom wound to specs for this instrument.

Ram’s Head Battersea Power Station Big Muff ₽i

    

When i was a Londoner, id often catch the 24 bus on sunday mornings from Hampsted Heath to its final destination, Pimlico. There was a pub there, next to the bus station where we would go have brunch and shoot pool. In the afternoon we would visit the Tate, usually.

And we would enjoy the haunting, post modern view of the abandoned Battersea Power Station from Pimlico.

Gilmour used a rams head Big Muff on Animals apparently.

Built for a friend on a pcb by OP ELECTRONICS, IT. Transistors BC239C from ebay seller, Whazzgroover. Sprague caps, etc

First time i mess with a hot glue gun, and i guess you can tell! 🐣

Electro Harmonix Vintage Black Finger 

This must be a very early one, word has it that Jimi Hendrix tried one of these boxes for its big muff-like forced sustain. It is one of the earliest electro harmonix effects. 

It is powered by TWO 9v batteries and so much for it “being distortion free”, it is very hissy and noisy, and colours the tone. The compression is VERY apparent and squashed.

Transistors: FS36999, the same as early 70’s Big Muffs.

       

The tube version Black Finger is a much different, more reliable and usable item.

Jh-1 Dunlop Jimi Hendrix Fuzzface

   Jim Dunlop holds the name FUZZFACE licence. Before it was spelled, FUZZ (space) FACE.

   Silicon BC108 transistors, vintage style build.

UPDATE BEWARE

Much to my surprise, and horror, the other day i decided to have a better look at the board. Well.. AT THE BACK OF THE BOARD, HIDING, it’s all SURFACE MOUNT TRIMMERS. EEEEEEEEEK!!!! This is the fakest pedal ever!

I decided to sell it right away. Although:

How does it sounds? Not bad in my opinion.. And the presentation is quite lush.

The Hendrix family on the other hand.. Geez they never got it with their son being a genius. And now that they can remix his oeuvre in the most appalling way, they went for it. 

I mean.. Has any of you listened to the reissued experience lps? 

Awful out of focus fx added, messy sound image (changes at every other track on the Are You Experienced lp), poor original sources research, no whatsoever idea of whats goin on: they managed to DESTROY even a song as straight forward as Fire! 

Idiotic panning solos? Yeah! 

Awful. 

And before you can say ‘man’, they put out the jimi hendrix fragrances. As if the world needed them badly.

So all in all this is possibly the only instance of the hendrix genius almost given a proper name.