Hello,

I have a Pioneer QX-646 that was given to me by my future father in-law. I have been using it quite often lately and will be tearing into it to clean the noisy controls. I also plan on replacing the aging electrolytics and have a few questions.

Which ones should I focus on first, those in the amplifier section, power supply, or the entire receiver?

What brands or type of electrolytics have others used or prefer? Will just any quality electrolytic cap work or is a "Black Gate" or other specialty cap better/worthwhile?

Any information will be greatly appreciated. I really enjoy using this receiver and want it to perform at its best. I also prefer it over my 7-year-old Kenwood.

Thanks,

Bobby

Proud owner of a TEAC X-1000R RTR, Sony TC-228 8 Track "Tapecorder" and a Pioneer QX-646 quad receiver.

Welcome Quad4Life!

The troublesome areas where things get noise are on the pre-amp/tone board and driver board. After cleaning all the controls and switches, that's where I would start. The few 949s i've serviced had noisy caps in the preamp, causing static and other background noise.

As far as caps go, unless you have some sort of miracle hearing capability, just about any brand of caps should be satisfactory -- especially if you're on a budget. Even cheap caps today far surpass the cap technology of when that 646 was new. i usually Get nichicon or Xicon --sp? (cuz is what our local dealer has) howeveri hear panasonic caps are pretty good for sound signal path applications.

What JP says.

Capacitors that are in the signal path will clean up the sound. The main power supply electrolytics will restore or enhance the machine's ability to deliver maximum power.

If you are going to buy a significant quantity, I recommend Digi-Key or Mouser. I like to use the 105 degree caps anywhere heat will be generated (power supply, power amps.)

On many Pioneers from the seventies, blue-colored Sanyo capacitors were used in preamp circuits and elsewhere (e.g. FM radio) -- in values from .22uF to 10uF. As far back as the mid-seventies, these devices began to fail. They liked to leak and turn into "capsistors."

Enjoy your machine!

Fred Longworth

Thanks everyone for the information. It will be very helpful. I was planning on going through my usual source, Mouser, which Fred mentioned. I will look out for those Sanyo caps Fred. :thmbsp:

I have another question in regards to replacement values. The goal is always to replace with the same capacitance and voltage values, but what if it is not possible. For instance, the main power supply electrolytic is 4700uF 50V. I have only been able to find in the Mouser catalog 5600uF 50v and 4700uf 100V. Is it better to go with the higher capacitance value or the higher voltage rating?

Once again, your help will be greatly appreciated.

Thanks,

Bobby

Proud owner of a TEAC X-1000R RTR, Sony TC-228 8 Track "Tapecorder" and a Pioneer QX-646 quad receiver.

If you are finding it hard to locate a specific value you might have better luck with digikey. They also might have a better variety of available stock in that range. As far as the United Chemicon 5600uf 100V goes, that would work fine.

Hello everyone,

I began taking a look at my receiver this evening to get a picture of what lies ahead. I noticed that all wire connections to the boards are wire wrapped around pins. What is the easiest way to disconnect and reconnect these wires?

The wires will have to be removed to work on the boards outside of the cabinet and I don't want a bad connection after the fact. Should they be soldered to the pins once everything is all said and done?

Thanks,

Bobby

Proud owner of a TEAC X-1000R RTR, Sony TC-228 8 Track "Tapecorder" and a Pioneer QX-646 quad receiver.

Use an unwrapping tool. This is what you looking for

http://www.specialized.net/ecommerce/shop/layout.asp?product%5Fid=122X725

SP is high so shop around.

This one is slightly cheaper:

http://www.elexp.com/pro_hh20.htm

Un-wrapping wirewrap is a last resort.

Hello,

I am putting together a list of electrolytic capacitors needed for the power supply and main audio signal paths in my QX-646. I will do the rest of the receiver later. I have been looking at getting either the Panasonic FC or Nichicon PW series capacitors, but have come to find that Nichicon has audio grade elecs in FW and FG series'.

What I would like to know is if there is a source for the Nichicon FW or FG series capacitors as they are not in any of my catalogs from Mouser, Allied or DigiKey.

Are the Panasonic FC's and/or Nichicon PW's just as good as the FW's and FG's?

Thanks,

Bobby

Proud owner of a TEAC X-1000R RTR, Sony TC-228 8 Track "Tapecorder" and a Pioneer QX-646 quad receiver.