So I paid £30 odd for this A-333 to restore and can't believe how thilfy it was. After a dry brush down I cleaned it with bicarbonate of soda mixed with distilled water. Now looks great.
I noticed two resistors were burnt out which I've replaced. I wanted to know what you think would of caused it? It's on the phono input.
I've recapped it now and really transformed the sound. Especially the power amp stage with new Panasonic/Nichicon caps and main filter caps well improved the bass.
I noticed two resistors were burnt out which I've replaced. I wanted to know what you think would of caused it? It's on the phono input.
I've recapped it now and really transformed the sound. Especially the power amp stage with new Panasonic/Nichicon caps and main filter caps well improved the bass.
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Also I want to replace these 4 resistors and want to make sure they are 4.7 ohms? It's hard to tell if the coloured strip is blue or violet. With the schematics having an exclamation mark inside the triangle I have to get it correct.
Much appreciate any input
Much appreciate any input
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Haha it stinked. First time I cleaned boards thoroughly by wetting it with distilled water mixed and drying with a heat gun. I forgot to picture it after doing that and recap but well impressed with the process 
it don't smell now.
Really made me appreciate the audio engineers out there as its a pain to pull apart. Luckily a section of bottom panel comes off to reach those 4 resistors
I'll go with 4.7s, they look like they been through some stress
Thank you MarsBravo!
it don't smell now. Really made me appreciate the audio engineers out there as its a pain to pull apart. Luckily a section of bottom panel comes off to reach those 4 resistors
I'll go with 4.7s, they look like they been through some stress
Thank you MarsBravo!
Hahaha your funny!
I have no 1 or 2 watt in that value. Yet was going to order 1 watt types. I'll check RS components for their 2 watt ones. The schematic says 1/4 or 1/2 watt unless stated. They are slightly smaller than the 1/2 watt resistors I have.
Do carbon or metal film handle heat better?
Well appreciate your suggestions sir
I have no 1 or 2 watt in that value. Yet was going to order 1 watt types. I'll check RS components for their 2 watt ones. The schematic says 1/4 or 1/2 watt unless stated. They are slightly smaller than the 1/2 watt resistors I have.
Do carbon or metal film handle heat better?
Well appreciate your suggestions sir
They will occasionally do so when not overloaded as well. Some amps are downright notorious for bad fusible resistors.
The burnt resistor next to CN17 would appear to be R299. That's a 10 ohm resistor connecting power amp input ground to chassis ground. Under no normal circumstances would this have any reason to blow up like it did, at least I fail to see any failure mode that would do this. (Service manual is on HiFiEngine.) Measure voltage across it, and if nothing substantial is found, replace the part and see what happens.
The 4.7 ohm resistors (R265 et.al.) are given as part no. RFA¼PS4R7J, so quarter watt 4.7 ohm 5% tolerance.
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Fantastic inputs guys.
The exclamation mark is in a triangle on the schematics but don't see any on accual resistor, apologies if I caused confusion but really good to know for the future, interesting.
Yeah R299 was replaced with a 10 ohm half watt, I'm surprised it worked previously while burnt.
I have the schematic from hifi engine. God send that site and a couple of others. Still unable to find service manual for the Denon PMA250 (Mark III) I've been working on though, need to set the bias.
The exclamation mark is in a triangle on the schematics but don't see any on accual resistor, apologies if I caused confusion but really good to know for the future, interesting.
Yeah R299 was replaced with a 10 ohm half watt, I'm surprised it worked previously while burnt.
I have the schematic from hifi engine. God send that site and a couple of others. Still unable to find service manual for the Denon PMA250 (Mark III) I've been working on though, need to set the bias.
Yes the IC sets the idle current.. this was a "non-switching" design Pioneer had during this era
Hahaha yeah swept it with a bible too!
The ICs are PA0016.
The reason I bought it is because I have a A-400 in prestine condition that I will recap as its been in its box for 20 years. Saved up for it when I was 11 with paper round money ha. Thought this will be a good exercise beforehand. May even use it to pre-amp it yet IDK.
Great thing to do (in theory) I don't usually get stuff with ICs as I'm a basic and a bit old skool at the moments.
They just seem to be unreliable and the reason equipment gets dumped.
I finally changed the resistors that were looking worse for wear and about 10 others while I was in there which measured out of their tolerance with one leg out. The 4.7ohm resistors I was asking about measured high, about 5.6-5.7ohms.
With the new caps and resistors I really restored its sound as it was very noisy.
Also replaced its binding posts, just for the reason of accepting banana plugs.
I've got a Pioneer A300x in the post I bought for £33 off ebay. It looks mint except the bottom panel is rusted so I'll swap the panels around from this A333 as the faceplate is tatty on this and sell the A300x on after cleaning up.
Just wanted to update the post to say thank you very much for your guidance. We'll appreciate it
With the new caps and resistors I really restored its sound as it was very noisy.
Also replaced its binding posts, just for the reason of accepting banana plugs.
I've got a Pioneer A300x in the post I bought for £33 off ebay. It looks mint except the bottom panel is rusted so I'll swap the panels around from this A333 as the faceplate is tatty on this and sell the A300x on after cleaning up.
Just wanted to update the post to say thank you very much for your guidance. We'll appreciate it
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