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Ampeg SVT VR Head requiring at least 115 volts from wall socket

#83
The transformers and power supply are very close on CL, VR, II, HD, and even the vintage units........
Click to expand...

Therefore I assumed the 300w and the 50w could be quite alike...
So, are you saying its impossible to rewire the primary side?, or DO a 40year old b25 have transformer with doubble winding on the mains?...


Btw; I registered for the forum today, so thanks for the warm welcome, JimmyM! :)
 
#84
Hey, Glenn...sorry...I totally misread your question. I thought you were talking about the relay mod that allows VR's to work with less than 115 volts. Then I just now see that you wre talking about the transformer wiring for European use. Sorry...it was in the subject line and I usually ignore them.

And welcome!
 
#86
Glenn, as Jimmy said, the rewiring procedure for the B25 is not the same. I've seen three different transformers listed for the B25: one with a 120 volt primary, one with a 240/120 dual voltage, and one with just a 240 volt primary. If you have the export model with the dual input primaries on the power transformer, it can easily be rewired. If not, you will need to buy a new power transformer or an external power unit that steps down the 240 volts to 120.


David
 
#88
If it is a dual primary transformer, it could have two extra wires taped off and tucked away. If there are any numbers on the transformer, you might see a model number PT-12-XA (used for both the single and dual primary models). The Ampeg part number for the dual primary power transformer was 300707-3. The secondary specs are 800 VAC CT @ 200mA, 5 VAC @ 3A, and 6.3 VAC @ 5A.

If you need to get a new transformer, they are very expensive. A dual primary model is available at fliptops.net for $165US ([Invalid or Expired Link Removed]).
 
#90
Thanks "Beans.."! Th thing is, Im soaking for a "not deadly heavy" substitute for my SVTCL. B25 seems to be almost impossbile to find here in scandinavia, so I was looking for this kind of info before buying.

Im also wondering; Could a vintage V4 or V4B also be a great choice, or are might to close to the weight of the SVT?

I love this forum by the way!
 
#92
The B25 weight would be perfect then.
I was a bit unclear, when I said "substitute" for my SVTCL. Im totaly aware of the difference in the output stage. I just want a solid rig for rehersales and for smaler jobs where I dont need earplugs/IEM. And yeah; A rig I can TRANSPORT WITH MY CAR! :)

With a B25 I may no longer "NEED" the SVTVR. My Hofner Violinbass deserves a real tonemachine sometimes...

Thanks for the info, guys! I now might just be able to get me one of these, and make it swing, at twice your voltage!... :)
 
#93
"110/120" volts is a catch-all label for standard US voltage. Any device available in the US should be designed to function in the range of 97 to 119 volts. The device may not perform to its full capacity at lower voltage, but it should run none the less. I think, if the "tech" is telling the truth, there's an issue with the design of the amp.
 
#94
hifibass said:
"110/120" volts is a catch-all label for standard US voltage. Any device available in the US should be designed to function in the range of 97 to 119 volts. The device may not perform to its full capacity at lower voltage, but it should run none the less. I think, if the "tech" is telling the truth, there's an issue with the design of the amp.
Click to expand...

did you read the entire thread? because we've already diagnosed and addressed the low votage problem 2 years ago.
 
#95
GlennH said:
Therefore I assumed the 300w and the 50w could be quite alike...
So, are you saying its impossible to rewire the primary side?, or DO a 40year old b25 have transformer with doubble winding on the mains?...


Btw; I registered for the forum today, so thanks for the warm welcome, JimmyM! :)
Click to expand...

The comment on transformers ONLY applies to the SVT family....... vintage, HD, II, 2 PRO, CL, VR. The basic design is similar or identical, depending on unit. but teh primary voltage varies.

The older units and ones of a different power can be anything.... Most old vintage SVT were 120V 60Hz units, but a dual primary type DID exist.

I don't know about the B25, I'd have to see if I have any data.

I owe someone else some old data too, and danged if I haven't forgotten to get it.. Somewhere I have noted what is wanted and for who........ I think it's a schematic.......

Anyhow, if you want to know about yours, the best way is to count primary wires..... 2 wires, single voltage. 4 wires probably 120/240 (115/230, whatever).
 
#97
I'm going to do the delay fix when my new VR arrives using a "1 into 2" connector onto #J27. I've read that a good way to discharge the capacitors is:

Turn Power switch On with the speaker connected. Wait a minute for warm-up and turn the Standby Off [the amp is now in normal playing position]. Wait a few minutes and turn the Power switch Off, but leave Standby Off [still in playing position]. Wait a few more minutes and turn the Standby switch to the On position.

Is this a good procedure to use?
 
#98
i would plug it in, play a bass thru it, and continue playing thru it while turning off the AC power to it (either unplug it from the wall, or turn it off with the switch on a power strip ( i use the power switch on my variac).
then wait about 15 minutes. this should remove most of the AC on the filter caps.
 
#99
slick_tu said:
I'm going to do the delay fix when my new VR arrives using a "1 into 2" connector onto #J27. I've read that a good way to discharge the capacitors is:

Turn Power switch On with the speaker connected. Wait a minute for warm-up and turn the Standby Off [the amp is now in normal playing position]. Wait a few minutes and turn the Power switch Off, but leave Standby Off [still in playing position]. Wait a few more minutes and turn the Standby switch to the On position.

Is this a good procedure to use?
Click to expand...

Here, if this helps, I did JohnK's mod in a thread.

http://www.talkbass.com/forum/showthread.php?t=617347&highlight=
 
#100
johnk_10 said:
i would plug it in, play a bass thru it, and continue playing thru it while turning off the AC power to it (either unplug it from the wall, or turn it off with the switch on a power strip ( i use the power switch on my variac).
then wait about 15 minutes. this should remove most of the AC on the filter caps.
Click to expand...

Thanks, I'll do that.



Rickett Customs said:
Here, if this helps, I did JohnK's mod in a thread.

http://www.talkbass.com/forum/showthread.php?t=617347&highlight=
Click to expand...

Thanks, I read JohnK's site; your pictures were helpful too.
 

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