Hi. Thanks for the response. Just re-read my last post and I can see how it could be seen as wanting to/doing that. What I was trying to say was that I turned the unit on and instead of leaving it in "standby" first, clicked the two stage power switch past the standby to "On".
Hence the "sparkles"...
Hence the "sparkles"...
Any tubes thas has had a "flash-over" is prone to do it again. The only cure is
to replace it .
I'm kind of curious here. You mentioned you re-capped it. Maybe someone already asked this but did you up the size of the power supply cap/s? Also, did it arc before you re-capped it? If you went too large on the filter caps I would guess that is your problem. Cary makes pretty good stuff and I just can't imagine an engineering problem on their end.
I haven't done any tube stuff in a long time but was wondering what would happen if the filament
supply to the 5U4s was a separate transformer and standby consisted of a power switch to the
primary side of the filament transformer. Would the cathodes be damaged during warm up?
G²
The 5U4's and most other directly heated tube rectifiers do not handle overly-large capacitors well.
This is specified in tube handbooks such as RCA's.
Using a sensible input capacitor of 47Uf is the preferred procedure.
As for stratus46's question, the 5U4 is directly heated - it has no "cathode".
This is specified in tube handbooks such as RCA's.
Using a sensible input capacitor of 47Uf is the preferred procedure.
As for stratus46's question, the 5U4 is directly heated - it has no "cathode".
This is the schematic to a different Cary integrated the SLI-70 - but there's some interesting information to be found; specifically the dual rectifiers, the series resistor right off the rectifiers and the enormous filter cap.
If I was going to fix an amp that had rectifier arcing problems and couldn't / wouldn't do it properly (I.E., a reasonable input cap and a choke...) dual rectifiers would get the job done, although very inefficiently. It does, however, have the rather attractive aesthetic change of an additional tube, which would quite likely make out more attractive aesthetically for the customers. A good thing, actually. 🙂 This schematic seems to have a couple mods done to it, and the 10R 10W resistor has probably been added to help with controlling arcing.
If I was going to fix an amp that had rectifier arcing problems and couldn't / wouldn't do it properly (I.E., a reasonable input cap and a choke...) dual rectifiers would get the job done, although very inefficiently. It does, however, have the rather attractive aesthetic change of an additional tube, which would quite likely make out more attractive aesthetically for the customers. A good thing, actually. 🙂 This schematic seems to have a couple mods done to it, and the 10R 10W resistor has probably been added to help with controlling arcing.
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That cary amp with those rediculously enormous filter caps is a goofy build by someone just as goofy.
Is that what these companies are building these days? - it's rediculous.
It's obvious that whoever designed that doesn't know or understand tube equipment.
Is that what these companies are building these days? - it's rediculous.
It's obvious that whoever designed that doesn't know or understand tube equipment.
i agree, i wonder if they even bothered to read the datasheets for the 5ar4, you just do not do it that way...
Whoa, not so fast on the ridiculous design assertions.
PSUD2 indicates the 5AR4 transient peak, and continuous peak, plate currents for 5AR4 may well not be exceeded for the schematic in post #49 (which is not even the OP's amp it seems). The parameter that is closest to being exceeded is the transient peak of 3.7A for the not so common hot turn-on event - and exceeding the spec would depend on the actual power transformer winding effective resistance and secondary voltage - the first peak of a hot turn on reaches 3.7A per anode for a 380V secondary with effective 50 ohm resistance, assuming a 500V B+ and 60mA loading.
As Eli points out back in post #4, if the tubes are not vintage or properly rated 5AR4 then that is a risk the amp owner bears. And there is also the operational issue of current sharing.
We are also up to 50 posts now, and no one has been advised of the actual schematic and operating values in the OP's amp.
PSUD2 indicates the 5AR4 transient peak, and continuous peak, plate currents for 5AR4 may well not be exceeded for the schematic in post #49 (which is not even the OP's amp it seems). The parameter that is closest to being exceeded is the transient peak of 3.7A for the not so common hot turn-on event - and exceeding the spec would depend on the actual power transformer winding effective resistance and secondary voltage - the first peak of a hot turn on reaches 3.7A per anode for a 380V secondary with effective 50 ohm resistance, assuming a 500V B+ and 60mA loading.
As Eli points out back in post #4, if the tubes are not vintage or properly rated 5AR4 then that is a risk the amp owner bears. And there is also the operational issue of current sharing.
We are also up to 50 posts now, and no one has been advised of the actual schematic and operating values in the OP's amp.
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> those filter capacitors aren't connected to ground.
Well, then there is no turn-on spike. No rectifier stress. No problem.
Well, then there is no turn-on spike. No rectifier stress. No problem.
I wonder if a CL140 on the centre tap would fix it? Probably not as well as adding a 10W 100R resistor on each 5AR4 plate...
afaik, choke input filters have far lower turn on surges than a cap input does,
caps have initial condition of being a short if uncharged,
coils are the opposite, open circuit at turn on....
caps have initial condition of being a short if uncharged,
coils are the opposite, open circuit at turn on....