Hello,
I am new to this forum, but have been reading all the threads about Dynaco's.
I am in the process of restoring my 416, I am the original owner, I bought this factory assembled amp, and it has not missed a beat over the years, I moved so many times over the years but I still used this amp as my main amp driving Bose 901's of which I also have owned a few from the Intercontinental to the latest iteration the series VI, and over the years I was always trading the older series for a new one at half the price of a new one, can't beat that deal. Bose loyalty owner program. To sum it up, it had enough juice to drive the 901's at any volume level I desired.
Anyways I decided to take the plunge and do a DIY restoration of the 416.
Every couple of years I would lube the pots and switches with contact cleaner and deoxit. I would also blow off and brush the dust build up inside the amp, do a visual of the wires, circuit boards and the big caps and check for any signs of leakage or burn outs. So far nothing yet.
So my question is should I replace some parts even though nothing is broken?
The good thing with this amp is there are a lot of parts and upgrade parts available. Those 2 big caps, I read up that you should use better ones like ones that are made in Japan (Nichicon / Nippon Chemi-con), Germany, France and USA. So is it a good idea also to use one with a higher voltage rating, as I have seen some Japanese made ones 12000uf 100V, the original ones were 10000uF 80V. I read on another thread to use one with a high ripple current and low ESR specs and for soldering to use silver solder ones.
Any advice is appreciated and will help me determine what I should do.
I know that the top and bottom panel and heat sink assembly will need refinishing and it looks like it's gonna be a long project that would take a few weekends of my time. Like any restoration always take pictures and tag and bag parts individually. I also downloaded some PDF files of the manual and the exploded views.
I have attached some pics of this amp.
I am new to this forum, but have been reading all the threads about Dynaco's.
I am in the process of restoring my 416, I am the original owner, I bought this factory assembled amp, and it has not missed a beat over the years, I moved so many times over the years but I still used this amp as my main amp driving Bose 901's of which I also have owned a few from the Intercontinental to the latest iteration the series VI, and over the years I was always trading the older series for a new one at half the price of a new one, can't beat that deal. Bose loyalty owner program. To sum it up, it had enough juice to drive the 901's at any volume level I desired.
Anyways I decided to take the plunge and do a DIY restoration of the 416.
Every couple of years I would lube the pots and switches with contact cleaner and deoxit. I would also blow off and brush the dust build up inside the amp, do a visual of the wires, circuit boards and the big caps and check for any signs of leakage or burn outs. So far nothing yet.
So my question is should I replace some parts even though nothing is broken?
The good thing with this amp is there are a lot of parts and upgrade parts available. Those 2 big caps, I read up that you should use better ones like ones that are made in Japan (Nichicon / Nippon Chemi-con), Germany, France and USA. So is it a good idea also to use one with a higher voltage rating, as I have seen some Japanese made ones 12000uf 100V, the original ones were 10000uF 80V. I read on another thread to use one with a high ripple current and low ESR specs and for soldering to use silver solder ones.
Any advice is appreciated and will help me determine what I should do.
I know that the top and bottom panel and heat sink assembly will need refinishing and it looks like it's gonna be a long project that would take a few weekends of my time. Like any restoration always take pictures and tag and bag parts individually. I also downloaded some PDF files of the manual and the exploded views.
I have attached some pics of this amp.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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While 40 or more years is a long time for elastomer sealed electrolytic caps to last, I have some good and bad news about the ones from my 1972 build ST120.
The 3300 uf 100 vdc labled "dynaco 284338" is reading 3820 uf & 5.8 ohms on an Atlas meter.
That is about 140X the limit ESR shown in the table of the meter.
OTOH the 3300 uf 60 vdc cap labled "dyna 283338 long life made in Scotland" is reading 3809 uf & 0.10 ESR. That is only 3x the standard reading.
The 500 uf 100 v cap labled "dyna 284507 long life made in scotland" is reading 534 uf, 0.16 uf and is in spec.
I like to install caps that have a long service life reading, since I had to replace the e-caps in my dynakit ST-70 four times in 46 years, for poor voltage out. Those were mostly local parts store caps, though the next to last cap came from the bankruptcy inventory purchaser Stereo Cost Cutters.
I prefer to buy from vendors that will tell me the expected service life in their selection tables. I've found in the US digikey has that in the table, and newark (farnell) you can ask for it. I've found that the caps I received from Panasonic, Nichicon, & Rubicon have been assembled in countries JAP, MAL, KOR, SPE, THA or USA. The ones I've received from United Chemicon have been assembled in a country that made the news this week for finding an entire town dedicated to producing fake seasoning additives bearing well known trademarks. The ESR of the long life caps I've bought from newark, mouser, digikey, since 2010, >3000 hours, have been adequate for my purposes. You may download the spec sheet of any cap you buy from the above distributors.
If you replace a screw terminal cap with a much cheaper "snap in" cap, one needs to make a transistion board to strain relieve the wires soldered on the terminals. This is a piece of insulating board with four holes drilled in it, two for the snap in tabs, two for the wires to loop through to avoid any stress on them should the solder joint heat up (as mine did).
You'll need at least a 35 W iron to solder to a 10000 uf cap, and a 100 or 130 W pistol would not be excessive.
Glue any snap in caps to the chassis to prevent it flopping around as you carry it. I use 3M windshield adhesive, but wall board adhesive in the lumberyard should also work well. You will find modern caps are physically a lot smaller than ones produced in the seventies. The steel clamps won't work and smaller replacements are not generally stocked.
100v caps instead of 80 is acceptable. If you go up from 10000 uf to 12000 uf you might consider putting a CL-xx NTC termistor in series with the primary of the power transformer to cut the turn on surge current. This goes after the switch and fuse. I mount them on cinch solder terminal strips, available mostly from tube parts houses like tubesandmore.com or triodeelectronics.com
You also might consider putting in a voltage surge arrestor (MOS) after the fuse, to damp out motor switch off voltage spikes and make an attempt to blow the fuse in case of a lightning strike down the line. I use 300 vac rated ones of the 15 mm or 22 mm diameter, which have a lot of energy reserve rating. These also go after the switch and fuse on a solder terminal strip. One goes between hot and neutral. In my location there are a lot of lightning storms, and not switching off the hifi while the television is disconnected from the antenna keeps the entertainment available with better sound than a battery radio.
I found my volume pots wore out a couple of times in my preamp. As this amp has some volume pots, you might also think about replacing them.
Cleaning of connectors from oxide on tin is certainly in order. You might even want to consider replacing the RCA jacks with gold plated ones as these are not tremendously expensive these days.
Have fun.
The 3300 uf 100 vdc labled "dynaco 284338" is reading 3820 uf & 5.8 ohms on an Atlas meter.
That is about 140X the limit ESR shown in the table of the meter.
OTOH the 3300 uf 60 vdc cap labled "dyna 283338 long life made in Scotland" is reading 3809 uf & 0.10 ESR. That is only 3x the standard reading.
The 500 uf 100 v cap labled "dyna 284507 long life made in scotland" is reading 534 uf, 0.16 uf and is in spec.
I like to install caps that have a long service life reading, since I had to replace the e-caps in my dynakit ST-70 four times in 46 years, for poor voltage out. Those were mostly local parts store caps, though the next to last cap came from the bankruptcy inventory purchaser Stereo Cost Cutters.
I prefer to buy from vendors that will tell me the expected service life in their selection tables. I've found in the US digikey has that in the table, and newark (farnell) you can ask for it. I've found that the caps I received from Panasonic, Nichicon, & Rubicon have been assembled in countries JAP, MAL, KOR, SPE, THA or USA. The ones I've received from United Chemicon have been assembled in a country that made the news this week for finding an entire town dedicated to producing fake seasoning additives bearing well known trademarks. The ESR of the long life caps I've bought from newark, mouser, digikey, since 2010, >3000 hours, have been adequate for my purposes. You may download the spec sheet of any cap you buy from the above distributors.
If you replace a screw terminal cap with a much cheaper "snap in" cap, one needs to make a transistion board to strain relieve the wires soldered on the terminals. This is a piece of insulating board with four holes drilled in it, two for the snap in tabs, two for the wires to loop through to avoid any stress on them should the solder joint heat up (as mine did).
You'll need at least a 35 W iron to solder to a 10000 uf cap, and a 100 or 130 W pistol would not be excessive.
Glue any snap in caps to the chassis to prevent it flopping around as you carry it. I use 3M windshield adhesive, but wall board adhesive in the lumberyard should also work well. You will find modern caps are physically a lot smaller than ones produced in the seventies. The steel clamps won't work and smaller replacements are not generally stocked.
100v caps instead of 80 is acceptable. If you go up from 10000 uf to 12000 uf you might consider putting a CL-xx NTC termistor in series with the primary of the power transformer to cut the turn on surge current. This goes after the switch and fuse. I mount them on cinch solder terminal strips, available mostly from tube parts houses like tubesandmore.com or triodeelectronics.com
You also might consider putting in a voltage surge arrestor (MOS) after the fuse, to damp out motor switch off voltage spikes and make an attempt to blow the fuse in case of a lightning strike down the line. I use 300 vac rated ones of the 15 mm or 22 mm diameter, which have a lot of energy reserve rating. These also go after the switch and fuse on a solder terminal strip. One goes between hot and neutral. In my location there are a lot of lightning storms, and not switching off the hifi while the television is disconnected from the antenna keeps the entertainment available with better sound than a battery radio.
I found my volume pots wore out a couple of times in my preamp. As this amp has some volume pots, you might also think about replacing them.
Cleaning of connectors from oxide on tin is certainly in order. You might even want to consider replacing the RCA jacks with gold plated ones as these are not tremendously expensive these days.
Have fun.
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Thanks for the infos. I found some really good ones made by Siemens of Germany, their Sikorel EPCOS line and they even had a screw in type and it is of the same diameter as the original Sangamo ones. Got the PS caps sorted, so what else should I replace? the other smaller caps? I did a visual check of the boards front and back with a magnifying glass and an led flash light and they all seem to be in good shape as these were factory assembled pcb's, I see no good logic in re-soldering every part as the boards might get damaged. Maybe I'd pop out the output transistors and put new paste in them.
Small electrolytic caps tend to deteriorate faster than the big ones due to the lower ratio of volume to seal area. I replace all mine once I start a project. The 1966-1969 organs had obvious sound deterioration due to dried up small electrolytics. Poor highs & lows. The Peavey PA amps had not so much obvious frequency effects.
Resoldering is not something I do unless I have a problem with popping noise.
The important part of the heat sink compound is the berylium oxide. The silicon grease can be totally dried up and the heat will still flow. I wouldn't mess with the output transistors.
All the Epcos parts I've received have been made in the country of rampant fakery. They were genuine since they came from Mouser, but we'll see if they last 40 years, compared to the Panasonic caps made in USA or Nichicon or Rubicon made in JAP MAL or THA. 4 years down and counting. Average life of systems I've been forced to buy from the country of fakers for lack of alternative sources - TV monitors and off the air tuners, PC supplies & displays - has been four years.
I played a global origin "Wurlitzer" piano last year- it was a joke. Totally incapable of playing soft notes with consistency. Wurlitzer pianos from NY state had premium actions and the high end ones had great sound.
Resoldering is not something I do unless I have a problem with popping noise.
The important part of the heat sink compound is the berylium oxide. The silicon grease can be totally dried up and the heat will still flow. I wouldn't mess with the output transistors.
All the Epcos parts I've received have been made in the country of rampant fakery. They were genuine since they came from Mouser, but we'll see if they last 40 years, compared to the Panasonic caps made in USA or Nichicon or Rubicon made in JAP MAL or THA. 4 years down and counting. Average life of systems I've been forced to buy from the country of fakers for lack of alternative sources - TV monitors and off the air tuners, PC supplies & displays - has been four years.
I played a global origin "Wurlitzer" piano last year- it was a joke. Totally incapable of playing soft notes with consistency. Wurlitzer pianos from NY state had premium actions and the high end ones had great sound.
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Got the caps from Teddss similar to Mouser, out of NC. So the stuff they sell are not fakes and sometimes NOS. I found this on the ebay, idk if it's worth upgrading to these or not.
DYNACO ST-400 ST410 ST-416 NEW PC-28 DRIVER BOARD KIT AS REQUESTED | eBay
DYNACO ST-400 ST410 ST-416 NEW PC-28 DRIVER BOARD KIT AS REQUESTED | eBay
So its a good idea to buy this cap kit from ebay?
DYNACO ST-400 ST-416 ST-410 PC-28 CAPACITOR KIT | eBay
After doing all these replacements do I need to adjust the bias for both channels?
DYNACO ST-400 ST-416 ST-410 PC-28 CAPACITOR KIT | eBay
After doing all these replacements do I need to adjust the bias for both channels?
About the e-bay cap kit: replacing the film caps is a total waste of money IMHO. Film caps last maybe 100 years. That is the top two rows of parts. And changing things that don't need it is hard on the board's lands. Some people like the sound of polyprophylene dielectric instead of polyester dielectric, but there is no description in the kit that those film caps are those either.
The electrolytic caps in the kit on the bottom row, who knows how long they would last? diyaudio people are really down on e-bay sellers, too many fakes and obsolete things. And there is no description that those are long life caps. From newark, digikey, you can select 6000-10000 rated e-caps (the small ones) without working too hard. Mouser sells the premium ones but they make you download the datasheet and read it to find them. Tedss, nobody here has said anything about it. I put too many bargain caps in the ST70 in four bouts over the years, to buy off the shelf "standard" caps again. Now that I can select the good stuff.
If your driver board still has TIP41C/42C as TO-220 drivers, you might get a little better sound with On Semi MJE15031/32 or 28/29. They are a little faster, 30 mhz Ft instead of 3 mhz.
Yeah, anytime I change anything I check the idle bias current. It went flaky on its own on the ST120. 220 ma instead of 40, good thing I checked it after I knocked a wire off with my foot. And any semiconductors you put in might not have been matched like factory screened batches are.
Look at your output transistors to see what they are. 400 khz in the ST120 was a sound limiter compared to faster Ft MJ802 of only 3 years later. More HF distortion on 400 khz output transistors. Don't know what you have.
I proved with the ST70 and the PAS2, that carbon comp resistors (the dark brown ones with the sharp edges and stripes) 100 kohms and over hiss more audibly than metal film resistors. I don't see any point any changing any carbon comp resistors under 100k that are in tolerance, but less hiss is good. Rounded edge cylinder resistors light tan & other colors are more probably carbon film and shouldn't be a hiss problem.
There is stuff in this forum about the obsolete Dynaco 4xx circuit with the op amps, I've read it but didn't bookmark it. Do some searching for ST400 ST410 ST416 articles with the diyaudio.com: prefix and see if you can find those threads. I'm not the expert on your amp; just I fix I lot of generic electronics (mostly organs) and like US made provenance.
The electrolytic caps in the kit on the bottom row, who knows how long they would last? diyaudio people are really down on e-bay sellers, too many fakes and obsolete things. And there is no description that those are long life caps. From newark, digikey, you can select 6000-10000 rated e-caps (the small ones) without working too hard. Mouser sells the premium ones but they make you download the datasheet and read it to find them. Tedss, nobody here has said anything about it. I put too many bargain caps in the ST70 in four bouts over the years, to buy off the shelf "standard" caps again. Now that I can select the good stuff.
If your driver board still has TIP41C/42C as TO-220 drivers, you might get a little better sound with On Semi MJE15031/32 or 28/29. They are a little faster, 30 mhz Ft instead of 3 mhz.
Yeah, anytime I change anything I check the idle bias current. It went flaky on its own on the ST120. 220 ma instead of 40, good thing I checked it after I knocked a wire off with my foot. And any semiconductors you put in might not have been matched like factory screened batches are.
Look at your output transistors to see what they are. 400 khz in the ST120 was a sound limiter compared to faster Ft MJ802 of only 3 years later. More HF distortion on 400 khz output transistors. Don't know what you have.
I proved with the ST70 and the PAS2, that carbon comp resistors (the dark brown ones with the sharp edges and stripes) 100 kohms and over hiss more audibly than metal film resistors. I don't see any point any changing any carbon comp resistors under 100k that are in tolerance, but less hiss is good. Rounded edge cylinder resistors light tan & other colors are more probably carbon film and shouldn't be a hiss problem.
There is stuff in this forum about the obsolete Dynaco 4xx circuit with the op amps, I've read it but didn't bookmark it. Do some searching for ST400 ST410 ST416 articles with the diyaudio.com: prefix and see if you can find those threads. I'm not the expert on your amp; just I fix I lot of generic electronics (mostly organs) and like US made provenance.
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No, you don't know the quality. Plus you're not getting much bang for the buck with that kit anyway. I wouldn't buy any electronic components from ebay if it can be avoided. Stick to sources such as Mouser, Digikey or Allied. B+D Enterprises is a good place to
find less obtainable semiconductors, they won't sell counterfeit devices. But I generally try to see if I can make a substitution through mouser and Digikey.
With a unit that old it should be checked anyway.
You might need this, good luck.
https://www.hifiengine.com/manual_library/dynaco/stereo-416.shtml
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Bottom base panel finally off all the parts
The ST-416 can be challenging to a DIY like me, but I took my time and did not rush taking everything apart, took a lot of pictures and marked the some of the parts and the orientation it was in.
I needed to refinish the bottom steel panel which imho was also heavy, they could have made it in aluminum, idk this might be a good idea in the future.
The PS main caps seem to still be in great shape, anyways I have some good replacements on the way so I'll keep these as spares as they are not broken or leaking. Need to order some thermal paste as well, any good brands or types?
As far as refinishing the top and bottom covers, the they have a gloss finish, textured type, Idk If I should have both panels powder coated or I'll just repaint them myself with good quality spray paint, like high temperature enamel paint that I use on my engine blocks, and prime as well before I put the final coat of black and cure them on an old beater oven I use for curing painted engine parts and accessories.
Here are some pictures I uploaded to Flickr.
https://flic.kr/s/aHskMZYAqg
The ST-416 can be challenging to a DIY like me, but I took my time and did not rush taking everything apart, took a lot of pictures and marked the some of the parts and the orientation it was in.
I needed to refinish the bottom steel panel which imho was also heavy, they could have made it in aluminum, idk this might be a good idea in the future.
The PS main caps seem to still be in great shape, anyways I have some good replacements on the way so I'll keep these as spares as they are not broken or leaking. Need to order some thermal paste as well, any good brands or types?
As far as refinishing the top and bottom covers, the they have a gloss finish, textured type, Idk If I should have both panels powder coated or I'll just repaint them myself with good quality spray paint, like high temperature enamel paint that I use on my engine blocks, and prime as well before I put the final coat of black and cure them on an old beater oven I use for curing painted engine parts and accessories.
Here are some pictures I uploaded to Flickr.
https://flic.kr/s/aHskMZYAqg
front panel
I think I overdid cleaning the front panel as the coating is gone. What did they use as a coating back then?
Photo 2017-01-16, 8 30 44 PM by Dave Pineda, on Flickr
I think I overdid cleaning the front panel as the coating is gone. What did they use as a coating back then?
Photo 2017-01-16, 8 30 44 PM by Dave Pineda, on Flickr
Krylon Clearkote comes to mind, but I haven't seen any in a store in 30 years. I never used it, my constructions are rude, crude, and abusable. Usually pulled out of the dumpster after their first life is over. I'm building a LM1875 amp now in a geophysical cable tester chassis I've been storing for about 40 years.
As I told you in post 2, old electrolytics go high ESR long before they ever leak. If you don't want to drop $99 + freight on an ESR tester from atlas, measure the watts out of your amp into 8 ohm 450 W resistors. P=V^2/Z where Z is the impedance of the speaker, 8 ohms. I use the ohmmite log resistors which are inductive like speakers. Also an analog VOM to measure voltage. My DVM produce random numbers on music; DVM AC scales are specified at 50 and 60 hz. If your power is low compared to spec, likely your rail capacitors are low value or more likely high ESR.
Furthermore, the elastomer seal in e-caps deteriorates on the shelf nearly as much as they do in sercice, due to the action of oxygen in the air. So you're not saving any life of your new caps by not using them. I've had e-caps leak and short on the third use, after a 25 year storage period waiting for me to find a source of new output vacuum tubes for the ST70.
As I told you in post 2, old electrolytics go high ESR long before they ever leak. If you don't want to drop $99 + freight on an ESR tester from atlas, measure the watts out of your amp into 8 ohm 450 W resistors. P=V^2/Z where Z is the impedance of the speaker, 8 ohms. I use the ohmmite log resistors which are inductive like speakers. Also an analog VOM to measure voltage. My DVM produce random numbers on music; DVM AC scales are specified at 50 and 60 hz. If your power is low compared to spec, likely your rail capacitors are low value or more likely high ESR.
Furthermore, the elastomer seal in e-caps deteriorates on the shelf nearly as much as they do in sercice, due to the action of oxygen in the air. So you're not saving any life of your new caps by not using them. I've had e-caps leak and short on the third use, after a 25 year storage period waiting for me to find a source of new output vacuum tubes for the ST70.
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Finally put it back together
Pics here:
https://www.facebook.com/PineappleRecords/posts/830397907098137
Pictures of the restore, it's finally done for now, breaking in the PS caps, hooked it up to a tuner playing at low level for a few hours, the fan never turned on at all and the heatsink was barely warm in my freezing basement.
😎
Pics here:
https://www.facebook.com/PineappleRecords/posts/830397907098137
Pictures of the restore, it's finally done for now, breaking in the PS caps, hooked it up to a tuner playing at low level for a few hours, the fan never turned on at all and the heatsink was barely warm in my freezing basement.
😎- Status
- Not open for further replies.