New Posts New Posts RSS Feed - Pioneer sa6200
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Welcome to the Graham Slee Audio Products Owners Forum

 

Open to all owners plus those contemplating the purchase of a Graham Slee HiFi System Components audio product and wishing to use this forum's loaner program: join here (Rules on posting can be found here)

This website along with trade marks Graham Slee and HiFi System Components are owned by Cadman Enterprises Ltd

Pioneer sa6200
 Post Reply Post Reply Page  12>
Author
  Topic Search Topic Search  Topic Options Topic Options
bass man View Drop Down
Regular
Regular
Avatar

Joined: 04 Apr 2016
Location: bolton dearne
Status: Offline
Points: 88 		Post Options Post Options   Thanks (0) Thanks(0)   Quote bass man Quote  Post ReplyReply Direct Link To This Post Topic: Pioneer sa6200
    Posted: 29 Sep 2018 at 9:06am
Morning 
Ive just aquired an old pioneer sa6200
Sounds pretty good but has a hiss from the left channel
Even with volume on zero 
I took the pre amp jumpers out and this hiss was gone so is in the pre amp ?
There is a bit of the old transistor smell 
Should be an easy one for graham 
paul
am from Yorkshire tha nuz
Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 16298 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 29 Sep 2018 at 7:00pm
Eyup Paul, naahthen, it's hoped tha dint shell aart too much fo't old thing?

The reason being that the old transistor smell is often the voltage amp transistor or even the output drivers getting hot in one power amp channel, and often the reason is because it has gone a tad unstable.

Removing the source (the preamp) removes what we can call its stimulus, and without a stimulus it might stabilise. And often this is because of slight oscillations on emitter-follower preamp outputs.

If it is the power amp on that channel it could be because the dominant pole capacitor has metamorphosized which ceramic capacitors of a certain age sometimes do. The answer would be to replace it.

Then again, it could be the preamp, or more likely its power supply. Here again a ceramic decoupling capacitor can morph into a low value resistor and load its voltage regulator making it hot and smelly. If the preamp has separate voltage regulators and one is hot suspect that.

The thing about electronics is nothing is as simple as we'd like it to be. Much as I'd love to offer practical help here (you being just down the road) I can't, because I've tons to do. You could ask John C via our contact form. He's always having broken amps dumped on him, and sometimes he gets them working again! Wink
That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
Back to Top
bass man View Drop Down
Regular
Regular
Avatar

Joined: 04 Apr 2016
Location: bolton dearne
Status: Offline
Points: 88 		Post Options Post Options   Thanks (0) Thanks(0)   Quote bass man Quote  Post ReplyReply Direct Link To This Post Posted: 29 Sep 2018 at 8:21pm
Cheers for that towd lad 
Im going to rip it apart n have a look
Only paid 40 quid for the old thing so can afford to treat it 
John c are you free Tongue
paul
am from Yorkshire tha nuz
Back to Top
Richardl60 View Drop Down
Senior Member
Senior Member


Joined: 04 Nov 2014
Location: Yorkshire
Status: Offline
Points: 1468 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 29 Sep 2018 at 9:16pm
Not sure how far away from Graham you are but if John C  cannot help there is a good electronic engineer in East Yorkshire 
Back to Top
bass man View Drop Down
Regular
Regular
Avatar

Joined: 04 Apr 2016
Location: bolton dearne
Status: Offline
Points: 88 		Post Options Post Options   Thanks (0) Thanks(0)   Quote bass man Quote  Post ReplyReply Direct Link To This Post Posted: 29 Sep 2018 at 10:25pm
Cheers richard 
I will give john a call tomora and see how busy he is
Anyway graham as tha got any books you recomend to enlighten me with electronics 
Its about time i did some homework 
Nuke
paul
am from Yorkshire tha nuz
Back to Top
BAK View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 Mar 2010
Location: Kentucky, USA
Status: Offline
Points: 1744 		Post Options Post Options   Thanks (0) Thanks(0)   Quote BAK Quote  Post ReplyReply Direct Link To This Post Posted: 30 Sep 2018 at 1:05am
 1. I would start by getting a schematic of the SA6200.
Even better, would be a service manual... some schematics have normal voltage measurements in key locations. (Some power supply PCBs have the major voltages printed on the board.)
I've been seeing many service manuals available on Ebay and other sites
 after doing a google search... some are free.
 2a. I would look for hot and/or charred parts
 2b. Then, I would replace all power supply electrolytics on any comercial unit over 20 years old... no question.
 3. Inspect all power resistors and power transistors for poor solder connections.
     (Hot parts weaken the solder joints.)
 4. Be aware that signal coupling capacitors can get noisy.
 5. Carbon resistors invariably increase in value after many years... even when not used.
     (Some increase as much as 50%.)
 6. Some transistors and op-amps can get noisy when everything else checks fine.
 7... 8... 9... 10... yes, there are more things to consider with a noisy amplifier.

 The above checklist is what I have used since 1970 in all electronics repairs
including: audio, TV, short wave, microwave, antenna systems, EEG, EKG, ventilators, dialysis units, data transmission systems, computers, telephones and systems, satellite systems, and more.......



Edited by BAK - 30 Sep 2018 at 1:06am
Bruce
AT-14SA, Pickering XV-15, Hana EL, Technics SL-1600MK2, Lautus, Majestic DAC, Technics SH-8055 spectrum analyzer, Eminence Beta8A custom cabs; Proprius & Reflex M or C, Enjoy Life your way!
Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 16298 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 30 Sep 2018 at 4:33am
Originally posted by bass man bass man wrote:

Anyway graham as tha got any books you recomend to enlighten me with electronics 
Its about time i did some homework 
Nuke


Amps are like cars in that they tend to follow the same basic structure, and the best author (so far) is Doug Self, who explains how each part of an amp works over these two books: Small Signal Audio Design (for understanding preamps) and Audio Power Amplifier Design. Some of it is advanced stuff because he's a (anti) distortion geek, but each stage of an amplifier is discussed in a very understandable way...

Unlike my ramblings on design https://www.hifisystemcomponents.com/forum/1970s-design-indulgence_topic4543.html which is not very well structured because I'm telling it as it is as I design an actual product (hopefully). It's a kind of diary as to what's being done over the period of time it takes.
That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
Back to Top
 Post Reply Post Reply Page  12>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.01
Copyright ©2001-2018 Web Wiz Ltd.

This page was generated in 0.113 seconds.