Friday Night Fun with a ST-70

sled108 · 6th February 2010, 03:25 AM

I just posted this on the Dynaco Tube Audio Forum, and on AudioKarma, but maybe it will help Someone here Too..

Having just thought that the FM Station that I was listening to had another "Technical Difficulty" I didn't give the Silence much Thought, until I turned to see that my ST-70 had gone Dark....SH*T...I turned it off, hoping that the Old Fuse had just had Enough...Well, I dug into it today and started by disconnecting the 360V Leads...Pop!! Goes the New Fuse...Double SH*T..I have read from Curcio's Repair Guide that this means One Thing..Bad Transformer...Oh No!!! Well, I then looked closer, and saw the 55v Bias Lead and pulled that from the Caps...Whaddaya Know...No Pop...Next, I Pulled the Caps and ran the 55v Straight thru the Diode and Resistor...Still no Pop..So then, I put all the tubes back in...No Pop, and now, Glowing Heaters. Hopefully I just had a Bad Cap. I'll know for sure when the New Ones get here...I don't have (2) 100V 47ufs one laying around...I'll let you know how it goes..

I can get all sorts of Mini Radial's from Parts Express...Would (2)100uf 100V do the Trick...Or, can I do Better?...Jeeze, the 100uf's are just .44 Ea....

Well, I did happen to have some Caps laying Around...(2)100uf 63V Gold Nichicon's...Yeah, I Know...Man, they are Small, 3/8" x 3/8"...But They Worked...They will at least hold me till I get some Better Ones. Thankfully it wasn't the PA-060...

HollowState · 6th February 2010, 03:58 AM

Be glad the fuse was the proper size and able to do it's job of protecting the transformer. I've more then once seen 10 or 15 amp "temporary" fuses that were never replaced cook a transformer. Btw, if you're in N. Jersey don't buy these parts from out of the country or even out of state when there are several local sources like Dynakit Parts in Clifton, Wayne Electronics on Rt.23 and Greenbrook Electronics on Rt.22.

sled108 · 6th February 2010, 04:06 AM

Hey, HollowState...Wayne Electronics is still Around? I loved that Place, but the last time I Flew By on 23 it looked Closed...Is it still there?.

HollowState · 6th February 2010, 04:18 AM

Quote:

Originally Posted by sled108

Hey, HollowState...Wayne Electronics is still Around? I loved that Place, but the last time I Flew By on 23 it looked Closed...Is it still there?.

It was when I was last there late last year. Probably November sometime. Give 'em a call. 973-839-5888 I hope they're still alive.
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Victor

sled108 · 6th February 2010, 05:11 AM

All Righty Then..Just got 6 x Nichicon 100uf 250V 105C Electrolytic Capacitors for $6.25 Shipped...That should do the Trick, with (4) to Spare...

sled108 · 6th February 2010, 06:02 AM

Oh, and they are coming from PA. USA...

6th February 2010, 03:25 AM	#1
sled108 diyAudio Member Join Date: May 2008 Location: Deep in the Heart of North Jersey	Friday Night Fun with a ST-70 I just posted this on the Dynaco Tube Audio Forum, and on AudioKarma, but maybe it will help Someone here Too.. Having just thought that the FM Station that I was listening to had another "Technical Difficulty" I didn't give the Silence much Thought, until I turned to see that my ST-70 had gone Dark....SHT...I turned it off, hoping that the Old Fuse had just had Enough...Well, I dug into it today and started by disconnecting the 360V Leads...Pop!! Goes the New Fuse...Double SHT..I have read from Curcio's Repair Guide that this means One Thing..Bad Transformer...Oh No!!! Well, I then looked closer, and saw the 55v Bias Lead and pulled that from the Caps...Whaddaya Know...No Pop...Next, I Pulled the Caps and ran the 55v Straight thru the Diode and Resistor...Still no Pop..So then, I put all the tubes back in...No Pop, and now, Glowing Heaters. Hopefully I just had a Bad Cap. I'll know for sure when the New Ones get here...I don't have (2) 100V 47ufs one laying around...I'll let you know how it goes.. I can get all sorts of Mini Radial's from Parts Express...Would (2)100uf 100V do the Trick...Or, can I do Better?...Jeeze, the 100uf's are just .44 Ea.... Well, I did happen to have some Caps laying Around...(2)100uf 63V Gold Nichicon's...Yeah, I Know...Man, they are Small, 3/8" x 3/8"...But They Worked...They will at least hold me till I get some Better Ones. Thankfully it wasn't the PA-060...

6th February 2010, 03:58 AM	#2
HollowState diyAudio Member Join Date: Aug 2006 Location: Taxland, New Jersey	Be glad the fuse was the proper size and able to do it's job of protecting the transformer. I've more then once seen 10 or 15 amp "temporary" fuses that were never replaced cook a transformer. Btw, if you're in N. Jersey don't buy these parts from out of the country or even out of state when there are several local sources like Dynakit Parts in Clifton, Wayne Electronics on Rt.23 and Greenbrook Electronics on Rt.22. __________________ "The supercomputer is technologically impossible. It would take all of the water that flows over Niagara Falls to cool the heat generated by the number of vacuum tubes required." ~ Professor of Electrical Engineering, New York University

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6th February 2010, 04:06 AM	#3
sled108 diyAudio Member Join Date: May 2008 Location: Deep in the Heart of North Jersey	Hey, HollowState...Wayne Electronics is still Around? I loved that Place, but the last time I Flew By on 23 it looked Closed...Is it still there?.

6th February 2010, 05:11 AM	#5
sled108 diyAudio Member Join Date: May 2008 Location: Deep in the Heart of North Jersey	All Righty Then..Just got 6 x Nichicon 100uf 250V 105C Electrolytic Capacitors for $6.25 Shipped...That should do the Trick, with (4) to Spare...

6th February 2010, 06:02 AM	#6
sled108 diyAudio Member Join Date: May 2008 Location: Deep in the Heart of North Jersey	Oh, and they are coming from PA. USA...

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