Audio Electronic Circuit Schematics

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timdrage
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Re: Audio Electronic Circuit Schematics

Post by timdrage » Mon Oct 08, 2018 3:18 am

Yes the one with the mini cartridge. Motor runs fine but the entire cartridge holder, tape heads and the cart itself broken beyond proper fixing, has been badly repaired over the years with wrong screws etc so nothing goes together properly any more. Had it kind of working in a nicely broken sounding way but like I say I think I need to hack some other tape mechanism into it.

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WhiteWarlock
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Re: Audio Electronic Circuit Schematics

Post by WhiteWarlock » Mon Oct 08, 2018 9:41 am

Image
Image
Image
Do you have this type of "Apollon tape"?
The top problem on those tapes with that unit is the "tape pressure pads"
do you have any squishy foam pads that IC chips are stuck on during shipping?
make replacement pads for keeping tape on tape heads......................
insert under tape in case.......................................
the old pads on those tapes disintegrate over time..................
you can hack something together even if it is simple tape loop in Apollon case
btw felt didn't work as well as IC chip foam
get creative when troubleshooting
best of luck
cheers

silly question time....
can you somehow mount the record/play heads so they make better contact with tape?
sounds like your Univox tape delay unit will function with some creativity from your description IMO

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WhiteWarlock
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Re: Audio Electronic Circuit Schematics

Post by WhiteWarlock » Mon Oct 08, 2018 3:40 pm

Awesome pedal perf/strip/pcb layout resource site:
http://effectslayouts.blogspot.com/


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timdrage
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Re: Audio Electronic Circuit Schematics

Post by timdrage » Sat Oct 13, 2018 1:30 am

Yep it's a that same kind of cartridge.l, totally broken tho. Ah the IC anti-static sponge idea is a good call. I've fixed 8-tracks before with some kind of window insulation foam tape stuff too
Can you somehow mount the record/play heads so make better contact with tape?
That was the plan but it's broken or loose in so many places that it barely functions :) I did try attaching a walkman temporarily and that seemed like it would work, I should properly rebuild soon that way :)

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WhiteWarlock
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Re: Audio Electronic Circuit Schematics

Post by WhiteWarlock » Sat Oct 20, 2018 11:55 am

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BOSS DR55 (Schematics/Manuals/Mods)
Image
DR55 does have an authentic sense of early 80s legendary nostalgia...
being BOSS' first DR-machine and also quite a successful early programmable drum machine.
It has been used by New Order, The Cure, Chris Carter, Sisters of Mercy, Chris & Cosey, Soft Cell and Thomas Dolby.

Boss DR-55: external trigger input mod

By default, the Boss DR-55 does not receive any kind of incoming clock. The ‘FS’ footswitch input takes a latching footswitch that starts and stops the existing clock, but that’s it. Although you can clock other equipment from the DR-55, it would be nice to be able to use an external clock to sync the Boss to, which would allow the Boss to trigger yet more devices with its CSQ and DBS outputs (active on Accented steps only and every step, respectively).

My mod as detailed here does exactly that. By replacing the existing FS jack socket, adding a small circuit, and replacing a jumper, we can safely trigger the DR-55 from an external trigger.

A quick internet search will turn up an existing clock input mod which is simpler to do and requires no extra parts; however, it puts the RAM at risk of damage from high triggers, and it does not sync the Boss’ own DBS output. It also requires ‘arming’ by hitting start before external triggering.

My own mod, though more complex, overcomes all these issues: the trigger input is protected, both the Boss’ trigger outputs maintain their correct functions, and triggering occurs without ‘arming’. The only two functional disadvantages of my mod are that you must set the Boss’ tempo to Fast, and to reset the pattern when stopped mid-way you need to remove the trigger plug. I’m going to blog another small mod which will overcome the latter inconvenience [EDIT: No I’m not! I sold both my 55s, thereby halting this particular project].
The Clock Modification in detail

Below is a diagram which shows everything you need to know about building this mod. Below that is a parts list. Key to this is the replacement FS jack socket; it needs to be TRS (ie. a stereo jack), with single pole changeover switches on the tip and ring contacts. I used a Lumberg KLBPSS3 (datasheet here, Farnell UK stock page here).

The additional circuit can be made very small indeed (3 rows * 8 holes on stripboard), and there is plenty of room for it inside the DR-55, particularly towards the right-hand end. The photos below illustrate my own placement.

There is one jumper to be removed, the one immediately to the right of the Variation switch. The replacement connections for the upper and lower point of this removed jumper are shown in the diagram, and you can see in the photos how I wired this up.

In brief: remove that jumper, solder the two points to two jack pins; build the extra circuit, and solder that to the jack and to the main PCB; replicate two of the pre-existing connections from the jack to the PCB. That’s it. I also stuck a small folded piece of card to the PCB to stop the extra circuit from shorting against components.
Boss DR-55 clock input mod

Image

Boss DR-55 clock input mod revised
Parts list:

1 * TRS 2-pole changeover jack socket – eg. Lumberg KLBPSS3
2 * 47k resistors – I used 1/8W for their smallness
1 * 10nF capacitor – I used a ceramic, again for smallness, but polyester film etc. would be usual
1 * 1N4148 signal diode or equivalent
1 * BC549C transistor or similar standard NPN

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Here’s the modified DR-55 (also incorporating my DC supply mod):
clock modded DR-55 overview

clock modded DR-55 overview

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And here’s a close-up of the clock mod:
clock modded DR-55 close up

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clock modded DR-55 close up

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How to use your new trigger input

The new trigger input will accept any positive pulse over a couple of volts. It’s edge triggered, so the pulse can be any length over a couple of milliseconds. The operating principle is to use the DR-55’s existing clock, but to gate it on for a very short duration; normally when the clock is gated off again, the pattern resets, but the new jack socket enables us to disable that by breaking the reset connection when a jack is inserted.

As I mentioned earlier, the Tempo must be set to Fast (ie. all the way clockwise) for correct function. This is because the DR-55’s clock, once triggered, finishes its pulse cycle. If this is longer than the incoming trigger cycle, it will ignore the new trigger; if we set the speed dial to its fastest, we can clock the DR-55 at any rate up to its natural maximum.

The pattern will cycle round as usual, but if you stop mid-pattern, new triggers will continue where they left off. To reset the pattern at this stage, you need to unplug the trigger jack and hit Stop. This is not ideal, I know, and I will be making an amendment to correct this later [EDIT: project halted, see above. I have no current plans to do any further work on the DR-55].

For now though, this mod works fine, as shown in the (slightly rubbish) video below:
Image

Boss DR-55: a 9V DC input modification


One of the drawbacks of the DR-55 as it comes unmodded is the power supply. In its original form, the DR-55 takes only batteries, and though this might be good for reducing cable clutter and having to find yet another wall-wart, it does mean you need to keep a regular stock of fresh AAs, and can guarantee that just when you want to use it, your DR-55’s batteries are too drained for the unit to function correctly.

Luckily, it is a relatively simple process to modify the DR-55 so that it takes a commonly-found 9V DC supply instead. I provide instructions for this below. It’s not the only way to do the job, but this is how I did it, and it works just fine. Modding the DR-55 in this way means it no longer accepts batteries, which means two things: 1) you will need access to a 9V adapter, and 2) pattern data will not be retained on power-off. Given that filling the memory of this humble machine can be done in less than five minutes, and I never use this outside my own home studio, I never found memory retention to be an issue. It would be possible to design a DC input that also catered for memory backup via battery, but I’m not going there.

There are two basic stages to this modification:

Making a 9V DC input: the basic voltage supply circuit
Installing the Mod: adapt some wire links on the output jack and PCB
Image

Because the DR-55’s RAM can be killed by voltages higher than around 7V, we take a 9V input and regulate it down to between 5V and 6V. I chose to use a 5V regulator propped up with a diode to give around 5.6V, but you could also use a 6V regulator and omit D2. The input jack I used is a 3.5mm mono minijack of the kind often used for audio and CV interconnects, mainly because I had lots of them and the holes are easier to drill than the larger ones needed for a plastic-bodied insulated barrel connector. Use whatever type you prefer, but note the polarity of your incoming DC, and don’t connect the +ve to the case… with a tip-positive 3.5mm jack, the sleeve of the input jack is connected to the shell of the socket, so it makes sense for that to be the ground. Some barrel connectors do likewise.

Here’s the schematic:
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Boss DR-55 DC input mod schematic

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Here’s the final circuit built onto stripboard. It will be panel-mounted using the socket:
DR-55 DC input build

DR-55 DC input build
Installing the Mod


Now we have a simple DC input, we could just solder the +ve and Gnd outputs to the corresponding solder points on the main board – that is, where the battery clip attaches. Black is ground, red is positive. This works, but you still need to insert an audio cable to turn the DR-55 on. I chose to remove that ‘feature’, as there are no longer any batteries to protect from accidental drain. It’s a simple mod that just means a couple of wiring changes.

The diagram below shows the required re-wiring. The audio output socket is wired by default to both ground and audio signal, as well as having two pins wired to act as a switch when a jack is insterted. We want to retain the audio and ground connections, but not the switch. We remove those wires and instead bridge the corresponding points on the PCB.

Image


Here’s a photograph of the full mod (note the wiring):
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DR-55 DC input wired and complete

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I damaged a track while desoldering the battery wires, which is why the red wire goes to the un-numbered hole next to point 9. They’re directly connected, happily.

Below are some photos of the hole I drilled for mounting the new DC input, and the final appearance when mounted and labelled with cheap Dymo (should have gone with black… oh well):
DR-55 DC input enclosure drilling
Image

So there you have it. My humble DR-55 now works from a regular 9V DC wall-wart supply, and switches on whether or not its audio is connected. The hardest part is putting the DR-55 back together again…

or you can just use old hacked (w/ 9v battery connector)phone charger from cheap Samsung 5v pay as you go track phone...
operating power range from the service manual for BOSS DR55 is 4.5v to 6v
Works for me!

next step external trigger inputs & outputs for each drum sound
http://manuals.fdiskc.com/flat/Boss%20D ... Manual.pdf

https://synthnerd.wordpress.com/2016/05 ... input-mod/
it's obviously not a TR808 or TR909 yet picked it up ages for $20 in the original box :P
replaced bad cd4011UB chip...
for getting the clock working on this old machine
was going to buy the CR55 DIY eurorack then remembered had this old gem buried around here :)
Last edited by WhiteWarlock on Sat Oct 20, 2018 7:20 pm, edited 5 times in total.

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WhiteWarlock
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Re: Audio Electronic Circuit Schematics

Post by WhiteWarlock » Sat Oct 20, 2018 7:05 pm

REDACTED
Last edited by WhiteWarlock on Sun Oct 21, 2018 8:04 pm, edited 1 time in total.

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WhiteWarlock
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Re: Audio Electronic Circuit Schematics

Post by WhiteWarlock » Sat Oct 20, 2018 7:07 pm

REDACTED
Last edited by WhiteWarlock on Sun Oct 21, 2018 8:04 pm, edited 2 times in total.

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WhiteWarlock
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Re: Audio Electronic Circuit Schematics

Post by WhiteWarlock » Sat Oct 20, 2018 7:08 pm

On my DR-55, in the bottom left (near the tone pot) there was a little trim-pot
which varied the kick decay, but on my friends there was only a resistor. Later
study of the service manual shows that only early serial number DR-55s have the
trim pot, so if you've a later rev. DR-55 here's the extremely simple way to
modify the bass drum decay..

The resistor is in the lower left of the circuit board (looking from above),
just below the tone control. 'BD' is stencilled on the PCB next to it, and the
resistor is over a little stencilled trim-pot picture. The following ASCII
diagram should help you locate the right resistor.

/-\
l l Tone Pot.
\-/
o
o
o ^
^==/ <<-- Resistor to be replaced.


Simply snip out the resistor, and replace with a horizontal trim-pot of several
K ohm. The trim pot goes between the three holes in the silly ASCII diagram
above, with the wiper terminal attached the middle/rightmost hole. I used a 2.2K
that I had floating around (what? your parts don't levitate like mine? freaky),
and that gave a reasonable control range...

Of course, I hold no responsibility for anything bad happening from this...
Last edited by WhiteWarlock on Sun Oct 21, 2018 8:06 pm, edited 1 time in total.

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crochambeau
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Re: Audio Electronic Circuit Schematics

Post by crochambeau » Sat Oct 20, 2018 8:33 pm

I get that you're excited about modifying your DR-55, but does that REALLY warrant posting text grab after text grab from an old mail group?

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WhiteWarlock
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Re: Audio Electronic Circuit Schematics

Post by WhiteWarlock » Sun Oct 21, 2018 6:43 am


Yes... considering this is an archival thread...
anyone doing web search on DR55 schematics/service manual/mods will find this info
(not that there will be many)
and for some reason my wordpress editor is fuct up right now...
so tried saving accumulated post on my site yet this was far less frustrating
(another thing for doing/solving on the list)
when have extra time will figure WTF and why my wordpress edtor toolbar vanished
and images don't show up plus text is white in the edit window
in the middle of other things at this current moment
needed putting the info somewhere for easy/fast web reference
plus the old hyper real posts are relevant information
it's not as if anyone else is posting schematics/service manual/mod info in this thread recently
it wasn't about as you put it all about being "excited"
more practical reason such as saving info in the middle of working on something...
easy web access in this thread so can review/add info if need be during project
BTW for anyone that is here actually researching DR55 mods...
The 5v phone power supply runs the saved pattern...
yet doesn't seem like it is enough voltage for writing pattern
the loading pattern LED stays on constantly in write mode
making edits doesn't change anything in pattern...
hmmmm
(running some more tests today plus recording the current patterns)
looks like time for digging through suitcases of power supplies for 6v PS
thanks for pretending you actually care :P

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Sleep Of Ages
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Re: Audio Electronic Circuit Schematics

Post by Sleep Of Ages » Sun Oct 21, 2018 7:45 pm

Crochie the Bandwidth Cop.

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WhiteWarlock
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Re: Audio Electronic Circuit Schematics

Post by WhiteWarlock » Sun Oct 21, 2018 8:21 pm

Image
repaired my wordpress editor...
REDACTED most of the old Hyperreal mod info...
posted that last night as backup before going to sleep when realized my WP editor was Bjorked


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crochambeau
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Re: Audio Electronic Circuit Schematics

Post by crochambeau » Fri Nov 16, 2018 7:16 am

Sleep Of Ages wrote:
Sun Oct 21, 2018 7:45 pm
Crochie the Bandwidth Cop.
It's easy for me to fill that role because I live in the sticks without access to broadband and just opening this thread has become an ordeal. (apologies on my delay in reply, I've been filtering my content as a result of user/bandwidth observations).
timdrage wrote:
Fri Nov 16, 2018 5:17 am




free ebook with some of this guy's schematics http://www.lulu.com/gb/en/shop/ko-tilma ... 38043.html
Thanks for the share, fun stuff to mull over, I want more scream. 1 amp at 30 volts, hahaha, that'll keep your tea warm.

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