Hi !
Recently i got this amp for a bargain, but as you may expected it did not come without problems. It looks like it have a case of bad corrosion.
Amp works fine, relay's work fine as well, tone controls.. But, when you give it a lil bit push (increase volume) some channel will start to hus and crackle (very low crackling mind you) and will drop in volume. This happens mostly on left channel, but other night it happend with right as well (when this happens, other channel is fine as far i can hear) also it doesn't matter where i increase volume, source, amp potentiometer.. How i fix this is I increase volume on amp itself, move pot up down up down, and it kinda returns to normal.. if volume is high it will start messing again.
Soo all in all, general imbalance of channels, and some hisses and crackles.
Now here is my plan on how to clean it:
1. Blow air from compressor to clean dust and other nasty stuff.
2. Use alcohol and tooth brush to clean any corrosion i see.
3. Use flux and soldering iron to get rid of really nasty corroded parts.
Anyone else some ideas / recommendations ?
Recently i got this amp for a bargain, but as you may expected it did not come without problems. It looks like it have a case of bad corrosion.
Amp works fine, relay's work fine as well, tone controls.. But, when you give it a lil bit push (increase volume) some channel will start to hus and crackle (very low crackling mind you) and will drop in volume. This happens mostly on left channel, but other night it happend with right as well (when this happens, other channel is fine as far i can hear) also it doesn't matter where i increase volume, source, amp potentiometer.. How i fix this is I increase volume on amp itself, move pot up down up down, and it kinda returns to normal.. if volume is high it will start messing again.
Soo all in all, general imbalance of channels, and some hisses and crackles.
Now here is my plan on how to clean it:
1. Blow air from compressor to clean dust and other nasty stuff.
2. Use alcohol and tooth brush to clean any corrosion i see.
3. Use flux and soldering iron to get rid of really nasty corroded parts.
Anyone else some ideas / recommendations ?
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See, thats the thing, problem start with volume levels, and ends with them. Today i tried again when same problem occurred to "fix" it by reducing and uping volume on source (my pc) and that kinda did the trick, but its much faster with amp pot (since gain is much higher)
Pot will need cleaning, thats for sure. Im just now wondering if maybe some caps are the problem ? As far i know, amp get hot and get more voltage and problems start.
Start with a process of cleaning all mechanical contacts (switches and pots) in the signal level circuits first. Make certain their contacts are clean and work reliably. Look for details of the volume control while you are in there, as this will, of course, have suffered the most wear and would be the most likely source of problems, if there are any here with the pots.
Your specific problem though, seems from your description to be the speaker relays. As the contacts become pitted, audio often becomes erratic (you may only hear something after raising volume, then suddenly full sound returns). If these these are a sealed type of speaker relay, they could well need to be replaced.
Only after you've cleaned and lubricated pots where necessary and you have the best results you can get for both channels, would you consider replacing the small electrolytic caps. Otherwise , you can't be certain of the effects of replacing caps, which may vary depending on what replacement parts you can find. Check the types, as some electrolytic caps used for audio coupling may be a special non-polarized type and they must be replaced with similar (NP) types.
Your specific problem though, seems from your description to be the speaker relays. As the contacts become pitted, audio often becomes erratic (you may only hear something after raising volume, then suddenly full sound returns). If these these are a sealed type of speaker relay, they could well need to be replaced.
Only after you've cleaned and lubricated pots where necessary and you have the best results you can get for both channels, would you consider replacing the small electrolytic caps. Otherwise , you can't be certain of the effects of replacing caps, which may vary depending on what replacement parts you can find. Check the types, as some electrolytic caps used for audio coupling may be a special non-polarized type and they must be replaced with similar (NP) types.
That is kinda exactly what is happening.
Any recommendation with what to clean and lubricate ?
I dont think main caps are problem, they look ok and not swollen, but i did notice in middle bottom part where small caps are one is kinda heavily corroded.
Whilst swollen caps are an obvious sign of long dead caps, they can also look fine and still be dead. Fluid heating and loss is the problem and no cap has a perfect seal that lasts forever.
An amplifier that is more than 20 years old and perhaps hasn't been used for long periods of time, needs to be checked and the capacitors probably need re-forming before it is powered up fully and the amplifier's performance should then be tested to assess whether it needs recapping. The electrolytics will mostly be fine if not subjected to abnormal heat and heavy use. As a rule of thumb, by 40 years, replace all electrolytic caps unless you can prove by ESR test that they are still fine.
An amplifier that works, is one thing but a one that works properly, sounds a whole lot better.
Switch contacts can be sealed or open and its not possible to clean every switch but those that are visible can be brushed and cleaned with pure alcohol.However, cheap industrial alcohol may also dissolve any paint marking on the PCB and components too, as it contains nasties to render it undrinkable. Isopropyl alcohol is usually more gentle and better at removing old grease. You can remove some boards completely and scrub with soap and hot water if solvent is hard to find. Remember, if using water, to rinse and dry in an oven at low temperature, before refitting.
Switch cleaner/lubricants are available from service supply agents. There are parts suppliers in most major cities that can help with such service aids. CRC is a leading brand, Kontakt 60 from Germany is just an example which should be fine but I can't buy European brands here in Oz: KOC WebSite: Maintenance and Repair products
An amplifier that is more than 20 years old and perhaps hasn't been used for long periods of time, needs to be checked and the capacitors probably need re-forming before it is powered up fully and the amplifier's performance should then be tested to assess whether it needs recapping. The electrolytics will mostly be fine if not subjected to abnormal heat and heavy use. As a rule of thumb, by 40 years, replace all electrolytic caps unless you can prove by ESR test that they are still fine.
An amplifier that works, is one thing but a one that works properly, sounds a whole lot better.
Switch contacts can be sealed or open and its not possible to clean every switch but those that are visible can be brushed and cleaned with pure alcohol.However, cheap industrial alcohol may also dissolve any paint marking on the PCB and components too, as it contains nasties to render it undrinkable. Isopropyl alcohol is usually more gentle and better at removing old grease. You can remove some boards completely and scrub with soap and hot water if solvent is hard to find. Remember, if using water, to rinse and dry in an oven at low temperature, before refitting.
Switch cleaner/lubricants are available from service supply agents. There are parts suppliers in most major cities that can help with such service aids. CRC is a leading brand, Kontakt 60 from Germany is just an example which should be fine but I can't buy European brands here in Oz: KOC WebSite: Maintenance and Repair products
It has been in use, since i bought it second hand, now i think previous owner didnt have these problems since he ran 8ohm speakers that are fairly week, as to opposed to mine 4Ohm speaker that will generate more heat and load. Or mabye he just lied, idk..
Now i do have a fairly small ultrasonic bath (20x20x30cm) I presume i can use that as well combined with hot water (is boiling water ok or no go ? )
Now i do have a fairly small ultrasonic bath (20x20x30cm) I presume i can use that as well combined with hot water (is boiling water ok or no go ? )
I haven't used an ultrasonic bath for this , so I can't say but the main board will be too large, I think. It won't hurt to begin with warm but not boiling water, though the ultrasonic excitation with a recommended non-foaming detergent for these baths, should be doing the work anyway.
People that sell an old amplifiers do so because it doesn't sound good any more or perhaps a partner is tired of the retro wireworks in the home. So an unwitting buyer has to fix the years of neglect, dirt, corrosion and worn parts before they hear good sound. It can be more expensive to restore some models than it's worth though - unless you are a collector, of course
People that sell an old amplifiers do so because it doesn't sound good any more or perhaps a partner is tired of the retro wireworks in the home. So an unwitting buyer has to fix the years of neglect, dirt, corrosion and worn parts before they hear good sound. It can be more expensive to restore some models than it's worth though - unless you are a collector, of course
I haven't used an ultrasonic bath for this , so I can't say but the main board will be too large, I think. It won't hurt to begin with warm but not boiling water, though the ultrasonic excitation with a recommended non-foaming detergent for these baths, should be doing the work anyway.
People that sell an old amplifiers do so because it doesn't sound good any more or perhaps a partner is tired of the retro wireworks in the home. So an unwitting buyer has to fix the years of neglect, dirt, corrosion and worn parts before they hear good sound. It can be more expensive to restore some models than it's worth though - unless you are a collector, of course
Yeah, main PCB is way to large, im just gona place it in plastic container with warm water and wash away
The dude who sold me is moving to apartment and he got these two active speakers he gona use soo thats the reason hes selling.
Im gona post detailed pictures and step by step stuff when i start cleaning this beast
Hopefully that should bring some insights - Status
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