Problem with noisy sammichSID + hot VR

[egmont01]

Hi, folks!

Another newbie here - after nILS got me hooked on the MIDIbox-project via another board a while ago I decided to start simple and ordered the sammichSID-Kit.

Soldering went faster than expected, but should i mention, that it took me about a week and two new MIDI-Interfaces to mess around with a "no tesponse from mios-core"-error until I recognized, that IC2 was waiting for installation between the bankstick-ICs...?

Anyway - now the Sidstation is working but a smaller issue still exist:

Switching through different presets gives me a backgroundnoise like surfing shortwave on cheap DX-radio. I 've attached a link to an example. As the noise differs from patch to patch I assume it is not a PSU-issue. Although I tried two different PSUs without success.

Any idea where to look for a mistake would be appreciated.

Last question: Whats a normal voltage-regulators/heatsink temperature? Just measured about 55 °C / 131 °F - way too hot?

My setup: sammichSID with two 8580R5, regulated linear PSUs 12V, 0,8A or 12V, 0,5A (center positive)

http://www.toofiles.com/en/oip/audios/mp3/mb.html

[m00dawg]

Some of those noises, while they are louder than they seem to be on mine, are just the nature of the beast. My 6581 in particular is one noisy dude. My 6582's are, by comparison, very quiet. The only thing I notice is small pops when loading or dumping patches and quieter ones when switching. I'm sure some of what you are hearing is also in my output, but I haven't noticed it much.

Since you have 8580's yours should be quieter than the 6581's and, in fact, I thought 8580's and 6582's were basically the same for the most part. You may want to check to make sure the SIDs functionally work (all the oscillators work, filters work, etc.).

As far as the temps, 55C is getting up there but a 12V linear-regulated wall-wart is what is typically recommended. The rectifier will drop the voltage a bit before it gets to the 7809 but the 7805 is just going to have to throw off a lot of heat. No good away around it on the Sammich since it was designed to be rather easy to build and one of the design trade-offs was using a simple wall-wart to power it (I assume anyway).

I heard about some folks trying to put a fan inside but haven't seen any pics or anything. You could doublecheck your thermal compound to make sure you have a sufficient amount (but not too much) so that the heat is being conducted into the heatsinks properly.

I'd be more worried about the SIDs myself :) I've been looking for very low profile heatsinks to use as the ones I used in the MB-6582 are too tall, but haven't found much.

[technobreath]

Just had å quick peek in the lm78xx vreg datasheet. Absoulute maximum operating temperature seems to be around 120 to 125 c.

With that said, u don't want it thaat hot in your case hehe. But for the vreg itself, it has automatic thermal shutdown, so it is hard to operate outside specs anyway. So its not too hot at all with 55c for the vreg, but as moondawg says, instead, worry about the sids ;-).

If u use a linear psu to power it with, the internal psu circuits will smooth it very well, but if u use switching psu, - that is another story. But its based on soundchip veeery old, so if it wasn't noisy I would worry hehe.

[m00dawg]

=sammichSID#sammichSID_power_supply]Here is the PSU I use for what it's worth.