Pioneer SX-727 Phoenix

[paul_ral]

I bought this receiver few days ago. The seller told me one channel is dead, somne knobs are missing. He send me two pictures and that is all

It as very, very dirty inside, I found some mud and rust on chassis

And now, a big surprise

I like the fuse style

I think it will be a hard restoration here!

 

[paul_ral]

Why Phoenix? Because of that

 

[EastPoint]

Whew, that’s a baaaaaaad one!

 

[merlynski]

WOW, hit by lightning?

 

[paul_ral]

No, hit by human stupidity. Somebody bypass the relay and the protection unit. Sad to see what poor repairs can do to a nice piece of equipment

I have checked voltages on power board. All are correct but how? A double diode is missing on that board but the answer is under

 

[paul_ral]

I pulled the old fuse bulb and replaced with led. I have to choose between blue and white warm led fuse.

Blue led

Warm white

I like warm white more, looks OEM.

 

[Oldsansui441]

I like warm white more, looks OEM.

I agree, the warm white is more original looking and much clearer. Pity that someone has stupidly bridged the relay and caused such damage , i'm sure you will get it back to a nice state. Are you going to try and source another driver board or repair what you have?

 

[paul_ral]

It is hard to find another 727 amp board. I searched on ebay but without succes. I found the big missing knobs in Germany and I ordered them. The small one is different from the other Pioneer series, like X3X. Inside the 737 knobs there are always white inlays for 4x4 mm quadratic switch axis, not black ones. Finally, I modified the inlay and I have all knobs now.
So my plan is to make a replica board. I have the old board, I have all sizes I need, I have the schematic and the layout.

 

[paul_ral]

BC177A in differential stage

Left channel

Right channel

Drivers: all transistors are good !!!

I am waiting for Mouser order now.

 

[paul_ral]

Trying to fix the holes with epoxy: step 1

 

[john stumpf]

your on the right track.i didnt think you were gonna try it so i didnt chime.the aviation navy used to use a clear epoxy mixed with powdered fibre glass .after all the burned material was excavated.they were picky on the board edge prep as they wanted a concave edge for mechanical strength. then a non stick backup was taped to one side. the favorite material was plastic coffee can lids. the trick was to just SLIGHTLY overfill the cavity as the excess had to be sanded off.then the board runs were replaced and the holes drilled.rather labor intensive.you must remember that carbon is a conductor.

 

[paul_ral]

Still waiting for my order. I recapped the heat amp board W21-002B. Before:

After: I use Nichicon KZ (MUSE), Nichicon KL and 6 KSC1845FTA transistors

 

[paul_ral]

New parts in, so 727 restoration continues

First i added new Littelfuse cartridge fuses 250V 0.5A - 0235.500MXEP and I changed all coupling capacitor using PW series.

Next was the PS board AWR-011A. I replaced: Q1 and Q3 with KSC2073TU and Q2 I used KSC2383YTA. All 5 caps were replaced with new PW ones with a little bump in voltage. I replace the plastic screws with metal ones and R3 330ohms 2W was replaced with a new 330ohms at 3W metal film resistor lifted on the board using ceramic sleeves. Ceramic capacitors were replaced with WIMA MKP10 , double diode 1S1850 with MUR1620CTG and D1-D4 SR3AM-4 with UF5405 lifted. Note the heated areas on board because of diodes and R3.

 

[paul_ral]

AF unit AWK-010. Before:

After cleaning

After recapping: Nichicon KZ, KA and KL in signal path. I replaced 2SA725 with KSA992 and 2SC1312 with KSC1845. All switches and potentiometer were cleaned

 

[leesonic]

Good luck with that project. Making a new board sounds interesting. I would also keep watching eBay to see what turns up. Do you look at every eBay site, as in eBay USA, England, Germany etc.? One might turn up somewhere in the World.

Lee.

 

[PE9ZZ]

You can instruct Feebay to also look in other territories. Look in the left side bar. I always do that from ebay.de

 

[paul_ral]

Yes I watch eBay daily, more I bought two missing knobs from Germany. The seller have one main amp board for 636 and I told him that I am looking for a 727. I found one in Brasil, this is the link for https://produto.mercadolivre.com.br...ficador-receiver-pioneer-sx-727-anp-081-b-_JM but I can not get in touch with the seller, I think is only for Brasil market.

 

[paul_ral]

The protection is done I'll post pictures with soon. It works again, the relay engages in 2 seconds after power up. It is good or need more time?
I need tour advice regarding caps type for tuner replacements. Should I go with KL or other? Thanks

 

[PE9ZZ]

If you hear a noticeable pop in your speakers after those 2 seconds it is too short, if it is almost nothing keep it. That may just be the input offset. You can verify with a multimeter. If it settles before those 2 s you're fine.

Do not touch the front end/IF strip. Otherwise, use whatever rocks your boat. I always use computer grade, lo-ESR, 105°C caps (Rubycon) but there is dispute about those. If you like to shell out money for upgrades that have no virtue by all means.

 

[paul_ral]

I used my Marantz 1060 as final, no pops, everything works fine. It needs more cleaning for volume potentiometer and selector switch. The sound is clear and warm I like how it sound coupled with my Marantz main amp.
I read here that KL serie is best choice for tuner recapp. I have all I need in hand, I don't want to spend a lot of money for caps. Two knobs - 28 euro shipped, replica board will be arround 100 euro.