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Hi, I hope this is allowed for the vintage asylum;
I have 2 Dynaco amps that sound beautiful. The Dyna70 and a Dyna35. When you get close to them you can hear transformer hum, something which Airtime said is absent from his recent Dyna build. My power plugs are the originals with no third prong for ground. Also both prongs on the old plug are the same size....today one is larger as you notice when plugging some thing in.
Am I doing something wrong?....What would be the easiest way to ground the amps. I will be using the basic 6 plug computer surge protector from a grounded outlet.....thanks....Mark Korda
Follow Ups:
Both of the Dynaco amplifiers have undersized transformers that run very hot. One can buy a much better ST70 transformer from Triode Electronics. I purchased a new power transformer for the SCA-35 but it was no better than the original.
So as Steve Brown indicated below, you can buy hardware to attempt to mitigate the vibration. However, I should caution you that power supply capacitors if they start to leak DC can stress the power transformer and the result will be more noise from the transformer as it tries to keep up with the current demands from the bad cap. If you haven't replaced the power supply caps, now would be a good time to do so. While the unit is on the bench I would definitely replace the power cord with a three prong grounded cable.
A quick check to determine if your chassis has voltage on it is to connect one lead of your DMM to the barrel (ground) of any RCA jack and the other to ground on your grounded outlet. Check for AC and DC voltage. If there is voltage on the RCA jack you will have current running through your interconnect cables between the two pieces of gear.
Hi Mark, Dynakit Parts has mounting pads to help reduce hum from the transformer. They also sell a new and IMHO much better transformer for all the Dynaco's. On the link I attached, the mounting hardware is down the page a bit.
you can tighten the 4 bolts on each corner of the trannies to tighten the lam stack, I would also see if any of the lams have the glue letting go and allowing them to vibrate, that would usually be the upper or lower ones. You may also find that using Q-dope, a high voltage insulating coating, will help the lams to keep from vibrating, only if they are flapping loose. I had a pair of power trannies on my Eico HF-30s that were mechanically pretty loud, I did all of this but it was the core buzzing, by using a pair of wedges on either side of the core as well as the above fixes I eliminated virtually all the hum, no buzz at all now (and the correct term is transformer "buzz" or buzzing when it is mechanical...)
Transformer hum is usually a mechanical noise that comes from the Lamination stack not being tight enough - not the compression at the four corners- though they should be tight - but the overall tightness of the stacking - having the 'E's & 'I's stacked so close that there is no gap.
typically if it is a vintage unit - there is not much that can be done-
short of Vacuum potting it -
Happy Listening
Hi Crazy and 6b, thanks I'll try tightening the bolts securing the bell trans covers.
One guy a few months back said the Dyna-35 cage was too short. I did install a new electrolytic cap and noticed some rust on top of a shiny new surface. The cage was touching the cap. I had put a cast iron York 5 lb. barbell weight on top of the cage and it stopped most of the hum. I will re-drill the cage screw holes.
With the ST-70 I'll see what goes,but 6b now I know what goes and Crazy I know from you how to better deal with it. The ST-70 was not plugged into a 6 unit power strip, yet but will be....thanks again...Mark K. PS. Crazy, you didn't used to do a skit with Jackie Gleason at the end of the show did you?
If you're a Gleason fan then you should get the "lost episodes". About 14 discs of the Honeymooners taken from the old Gleason variety show prior to and after the "classic 36" episodes.
Great stuff with all the screw-ups and ad libs uncut and aired LIVE!!!! All those cheesy canvas sets and still they pulled off some of the best comedy ever recorded.
Unfortunately the humming trannies there isn't a lot you can do. You could try tightening the bolts holding the laminations. Some people revarnished them to "glue" them back together. the only thing that works is a big heavy ass weight sitting on them.
My first ST-70 had that problem REALLLLLL bad!!! it was so loud that I could here it across the room with the music on at a "good" level. I eventually had to sell them because I couldn't take the noise anymore.
charles
Thanks Airtime and all you guys! You have answered my question and then some.
Heres some tough trivia......What food order did Jackie Gleason order on the run when playing Buford T. Justice in Smokey and the Bandit 1. Hint; His beverages were 2 Dr. Peppahs....Mark K.
" Now that's a vintage plug
A friend you get for nothing,an enemy has to be bought
Hi Mike,
Amazing how close it looks to a modern sparkplug.
Dave
I noticed that as well.
A friend you get for nothing,an enemy has to be bought
FYI... It was Frankie Fontaine doing Crazy Guggenheim.
.
I did not do a skit with Jackie Gleason, but I did watch his show. Maybe it is still affecting me!
Dave
Bad grounding would come out of the speakers. If the sound is coming directly from the transformers, it is vibration, not grounding. Some old transformers hum some don't. It is fairly common with the old Dynaco transformers. In the 80's when I was running a pair of Mark IV's, I heard of people putting wood spacers between the transformer and the chassis to damp the vibration. There are probably more sophisticated ways to damp them. Me, I just let the transformers hum along with the music. I figured sooner or later, they would learn the words.
Dave
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