I found this MOV on ebay listed for 3.75 best offer free shipping. It seems like it would do the job and then some hopefully. Or am I misunderstanding the values of clamping voltage and other ratings?
GE Littelfuse- Radial Leaded Varistor V1000LA160B 1000VAC MOV Metal Oxide
http://www.littelfuse.com/products/Varistors/AC+Power+Protection/LA/V1000LA160B.html
GE Littelfuse- Radial Leaded Varistor V1000LA160B 1000VAC MOV Metal Oxide
http://www.littelfuse.com/products/Varistors/AC+Power+Protection/LA/V1000LA160B.html
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A MOS varistor doesn't begin to act until the nominal voltage, thus a 1000 VAC varistor allows motor spikes on a 120 VAC line right through without supression. See this at Mouser in TX, V14E230P Littelfuse Varistors
for $.34 each. Nominal DC voltage 300, clamp voltage 595, 14 mm size like a motor drive has. Your transformer wiring should be able to stand 595 v. As far as the $9 USPS priority shipment cost, tack the varistor onto the order for the capacitors. You want the capacitors rated at 1000 v, that is the voltage where they might break down, and you don't want the capacitors breaking down, as it is permanent, leaving a short circuit. MOS varistors are designed to break down over and over again and when they wear out they frequently are open.
I see you are in FL, Newark is closer at NC. Whichever, if you're receiving at a house, select USPS shipment to avoid the residence surcharge from UPS or worse, FedEx. I get UPS business rate, which is cheaper over short distances, ~$6 for 2 pounds. FedEx treats me as a residence, double charge at $13 minimum. USPS is $6 or $9 depending how much packaging they use.
for $.34 each. Nominal DC voltage 300, clamp voltage 595, 14 mm size like a motor drive has. Your transformer wiring should be able to stand 595 v. As far as the $9 USPS priority shipment cost, tack the varistor onto the order for the capacitors. You want the capacitors rated at 1000 v, that is the voltage where they might break down, and you don't want the capacitors breaking down, as it is permanent, leaving a short circuit. MOS varistors are designed to break down over and over again and when they wear out they frequently are open.
I see you are in FL, Newark is closer at NC. Whichever, if you're receiving at a house, select USPS shipment to avoid the residence surcharge from UPS or worse, FedEx. I get UPS business rate, which is cheaper over short distances, ~$6 for 2 pounds. FedEx treats me as a residence, double charge at $13 minimum. USPS is $6 or $9 depending how much packaging they use.
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thanks for the offer, it's really decent of you. I'll try indiannajo's parts source again. I don't mind spending some cash on this amp. I got it for 50.00 because the guy broke the input jack and his cat used the carpet covering for a scratching post. It's only 2 years old and otherwise perfect. I went for 450.00 originally. thanks again for the offer. I like the idea of knowing whether the mos is still working. Is there an IC that controls the led?
will that one work with 120vac line or is it for 230v and I wonder if it would be a better idea to eliminate the two caps to prevent shorts, that is if the noise isn't too bad.
here's the part that's across the power switch.
An externally hosted image should be here but it was not working when we last tested it.
Is it to stop a thump during power up/off? I had a Hafler G300 amp that had a brutal thump when powered up even with the volume off. Scary for the spkrs sake.
Sorry, I was mistaken actually. Just dug it out of the bin and it looks like the LEDs are for AC live (yellow) and ground (green). It has three 15mm MOVs; one from live to neutral and one each from live/neutral to ground. Also has two film caps from live/neutral to ground.
You are still welcome to have it even if you just want to remove the MOVs from it. I also have a few 100nF ceramics I pulled off a power supply but they might only be 50V.
Attachments
thanks for offering those. I've seen a schematic that uses three like that. Do you think they're the 300/595 clamping voltage type? I'd rather be safe than sorry with all the voltage fluctuations and spikes here in FLA. The way this thing blew the caps is starting to worry me about every thing I own. I own a ton of music gear that hopefully the Furman PL-8c is capable of protecting.
Clemford,
No, a power-off thump is usually caused by the power supply caps discharging with the speakers connected, as in the speaker relay (if any) isn't working. The cap across the switch contacts is to minimize arcing of the contacts, although it may also reduce the popping noise associated with switch contacts.
Mike
No, a power-off thump is usually caused by the power supply caps discharging with the speakers connected, as in the speaker relay (if any) isn't working. The cap across the switch contacts is to minimize arcing of the contacts, although it may also reduce the popping noise associated with switch contacts.
Mike
For 120Vac mains,I usually see/use 130-150V MOV's. You want it a bit higher than the mains voltage,so it doesn't clamp constantly,but not so high that it lets all kinds of nasty spikes through. 300/500V is way too high,IMO.
Here's a couple suitable candidates
150V: V150LA10AP Littelfuse Inc | F3017-ND | DigiKey
140V: V140LA10AP Littelfuse Inc | F3016-ND | DigiKey
130V: V130LA10AP Littelfuse Inc | F3015-ND | DigiKey
Here's a couple suitable candidates
150V: V150LA10AP Littelfuse Inc | F3017-ND | DigiKey
140V: V140LA10AP Littelfuse Inc | F3016-ND | DigiKey
130V: V130LA10AP Littelfuse Inc | F3015-ND | DigiKey
if that's the case, I think radio shack has them for a couple of bucks in store.
that's why I was wondering if I could use the mylar ones in place of them but I guess they are more for tone rather than filtering? Of all the schematics I found on line I don't think many put caps on the primary at all. Seems like they are more trouble than they're worth. I would think there's less chance of shorting the primary to ground without them.
i think that's the reason why Indiannajo said to use 1kv ones. Good insurance in my book if I decide to use them. I think when I get the replacement input jack i'll see how the amp performs without them though.
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