The ghetto mod thread

[stj]

Re: The ghetto mod thread

i have seen rubber used.

problem is, even rubber will harden & crack eventually.

[SteveNielsen]

Re: The ghetto mod thread

Yes but certainly not as quickly as the foam does. Foam also has more acoustic transparency than solid rubber and in my mind foam would seem to allow a certain amount of back-cone radiated sonic energy to mix with front radiated sound out of phase.

[momaka]

Re: The ghetto mod thread

I wonder if someone could come up with a different material to use for the cone edge surround besides the crappy foam, say a thin solid rubber surround like a bicycle inner tube is? I think the paper surround is promising.

Hi-end car woofers usually come with rubber surrounds (or rubber-like, at least). IIRC, the rubber doesn't provide acoustic damping as good as foam. However, it is a bit tougher, so it allows more power to be pushed in the speaker (which, if you've seen videos of car woofers flexing hard and playing loud, you will understand why - foam would likely rip apart at those power levels).
See this one, for example:
https://www.youtube.com/watch?v=XrVSj0WwtMM

And here is someone's home-brew version :
https://www.youtube.com/watch?v=C2k3jE4kqKE

Other material I have seen used somewhat often is rubber-impregnated cloth. But I'm not sure how good of a material that is for high-power speakers - especially woofers.

The ones I saw with cloth surrounds were a little "soft" - i.e. it was easy to move the speaker cone. Ironically, with both of these instances, the speaker enclosure was a ported design. From what I've been reading, soft surrounds are better fit for sealed enclosures, since ported and transmission line (T-line) enclosures don't provide any means to limit the cone movement below their tuned frequency, which means the speaker can easily bottom-out and possibly get damaged.

Anyways, the Cewin Vega speaker above, along with my other CV drivers all have datecode stamps from early to mid 90's and all are with completely rotten foam surrounds. I think oldest one is a '92 or '94, and youngest is '96 or '97. So more or less, that foam has lasted probably about 15 years (I'm not counting the last few, because the foam probably started to rot badly then). This isn't too bad overall, IMO.

Still, I think rubber is better. The Sony SS-MB215 floor standing speakers I use in my room as monitors use rubber surrounds on the woofers. My family got these speakers back in 2002 or so from Sears (so they are close to 14 years old now). The rubber is still good on them today with no signs of hardening anywhere.

Did you use anything like the old school speaker dope to kind of "vulcanize" the paper?

Nope, I haven't.

Ever since I fixed the Realistc Nova-18, however, I have been thinking about coating the paper with latex paint. I figured latex is fairly rubbery and we already have a few cans of leftover interior latex paint anyways, so might as well try it. I will most likely test it on the paper surround of the CV speaker above. Probably next week or so. Will let you know how it goes.

[Compgeke]

Re: The ghetto mod thread

Found this in a C64 with ram problems. Pin1 was cut, but still not that great of a fix.

[stj]

Re: The ghetto mod thread

i hate that trick, it causes excess loading and wont help if an input or output is shorted on the old chip.

[Compgeke]

Re: The ghetto mod thread

I do as well. Makes it harder to diagnose when you find something like that and you don't know if that's the cause or something else is bad and they tried that as a fix that didn't work.

Piggybacking is only something I do for diagnostic, like stack a 2nd 4164 on top of one of the existing ones to see if that chip's bad. Very useful trick for old computers, saves a lot of time from desoldering all the chips and soldering in sockets then swapping until something works.

[stj]

Re: The ghetto mod thread

most dram failures cause the output to stick,
you can spot them with a logic probe.

that and the burned-finger test

[momaka]

Re: The ghetto mod thread

Found this in a C64 with ram problems. Pin1 was cut, but still not that great of a fix.

Now that's what you call chip pr0n
(I guess that's where the piggyback term originates from? )

[Agent24]

Re: The ghetto mod thread

Probably they did it for a quick test and it worked, so they left it like that to save time.

Of course if I was now trying to troubleshoot it, I'd remove both chips and replace with a socket.

[goontron]

Re: The ghetto mod thread

I had two dead acer aspire netbooks. I made one with the good parts. Blue one had a good everything but display and SDcard slot. The red one had a bad motherboard, no ram, no HDD. I put the red display on the blue unit and put the SDcard slot in it too. The touchpad buttons on the blue one had gouge in it, so I put the red one in its place. It's complete with a bodged in 64gb SSD and a crap looking (internally good. Protected well. LG cells!) Battery. It also has a RTL8188 N wireless in place of the atheros G wireless.

[dragos2009]

Re: The ghetto mod thread

by the way i really like the look of that acer goontron looks really nice like a custom job

[goontron]

Re: The ghetto mod thread

One thing i didn't notice was the display hinge end pieces are one blue and one red.

Unrelated links that i will need later: http://www.hddoracle.com/viewtopic.php?f=2&t=276
http://www.hddoracle.com/viewtopic.php?f=100&t=155

[eccerr0r]

Re: The ghetto mod thread

Found this in a C64 with ram problems. Pin1 was cut, but still not that great of a fix.

Now I'm not an expert at C64 hardware as I've never owned one, but it also could be possible it wasn't an aftermarket fix, but rather a design fix. I'd imagine if it was an aftermarket fix, pin 15 needs to be cut. But as a design fix, possibly the output of the LS257 simply didn't have enough drive strength and the quick fix was to use two (assuming the inputs aren't loaded down too much.)

Design fault, yes, alas, if it works, it works. I'd be worried if just pin 1 was cut as a repair... pin 15 must be cut as a repair...

[Agent24]

Re: The ghetto mod thread

From the photo it looks like Pin 16 (Vcc) was cut on the old chip. Without power I don't see how you'd get extra drive current though, so I doubt that's why the new chip is there.

Both Pin 1 and Pin 15 are inputs. I don't see how cutting either of those would make sense. Pin 15 is for disabling the outputs, but only when pulled high. Unless you hoped it would float high (probably a bad idea).

But why would you set the outputs disabled on a faulty chip? Who says it would disable them anyway?

[stj]

Re: The ghetto mod thread

commodore dont do that, all pcb revisions are error free.
the only change to the 64 was to add some diodes to the serial port, and that resulted in a pcb change.

[eccerr0r]

Re: The ghetto mod thread

hmm... hard to tell if pin 16 was cut... that may do more for disabling the old chip, but it would still leak. Not sure why they simply remove the old chip. If they were cutting pins, might well just cut all of them to stubs, take off the body of the old chip, and solder the new chip to the stubs?

[stj]

Re: The ghetto mod thread

pin16 is the 5v supply.

[stj]

Re: The ghetto mod thread

If they were cutting pins, might well just cut all of them to stubs, take off the body of the old chip, and solder the new chip to the stubs?

i'v seen that tried and had to clean up the mess for the owner,
Atari used to recommend it!!

when you try to solder to the stub it becomes loose and flops around - usually ending up stuck to the one next to it!

[SteveNielsen]

Re: The ghetto mod thread

Found this in a C64 with ram problems. Pin1 was cut, but still not that great of a fix.

I've seen that on a few boards as well back in the 80s. Not limited to any particular brand as I recall, it was just done and if it worked then it was left alone. Shitty practice but it happened.

[eccerr0r]

Re: The ghetto mod thread

I guess once you cut off the plastic of a soldered DIP, it should be fairly easy to remove the remaining pins one by one especially if it becomes loose and flops around... Still don't get why it was stacked other than for drive strength!