I recently brought a Sanyo MR-999 R2R tape deck online and am having issues with it. It likes to make hissing\popping noises whenever it is in play but it also happens occasionally when I put it into record mode. What could be the source of this as I am thinking its ether the original capacitors, leaky\noisy transistors somewhere in the record\play head amplifier or the record\play switches being dirty (even after giving them a good cycling through by engaging play and record a few times).

Any help is greatly appreciated

More likely a noisy resistor, unless they are film types. Carbon comp parts are notorious for this.

You can track it down by clipping in a 100nF cap to ground, starting at the base of the first stage.

There are also often black sometimes brown etc. plastic axials around 3/8" in diameter and 1/2" long common in car radios & lots of other stuff. These horrid little beasts can crack their jackets, burn & generally create havoc.

Keep an eye out for them; Not unusual to decorate the bin with all of them, from a set.

Marc

I was planning on replacing the caps anyway as the one for the motor gets hot to the touch after its been running for around 5-10 minutes. I have managed to get my hands on a partial service manual (no schematic but it comes with a parts list and board layout as well as a troubleshooting checklist) and it appears that they are "Carbon P and Carbon L" types. Are these the same as carbon comps?

Schematic is freely available from here: https://elektrotanya.com/sanyo_mr999.pdf/download.html

Use the bypass cap method to track down where the noise is coming from rather than guessing and shotgunning the thing.

I got my hands on the schematic and will definitely be using the bypass cap method to fault find. For the resistors in the service manual, they are listed as being "Carbon L and Carbon P" types. Are these the same thing as carbon composition?

Don't know. The "quiet" type is normally a carbon film resistor. These normally have little bulges (end caps) where the wires are attached.

There has been a variety of resistors made over the years, some more successful than others. Cracked carbon was interesting, my running gag with them was that they kept cracking & went high. As there is an erase oscillator there could be Mica caps & they often have a "hissy fit" when they die.

Early Germanium transistors had a habit of hissing, especially the output ones.

White space fixed known cause.

Hopefully someone can get of the enormous amount of white space.

Thanks.