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David Farber <farberbear.unspam@aol.com>: Sep 20 03:36PM -0700 This Carvin B2000 bass amplifier was brought to me with the problem that it wouldn't turn on. The user said it was working fine until there was a bright flash that could be seen through the front grill. Then it went dead. I opened it up and found a very fried and crispy looking disc which I think is an MOV. It's labeled TR1 on the "main board close up" as seen in these pictures. You can see by the photo it parallels the (removed) relay's normally open contact (AC out?) and the common, AC in contact. Photos are here, https://app.box.com/s/ch670hnsrtoswqhebtrye95n2vw5ktre   The other photos are to give you a general idea of what the board looks like. The reason I took photos of the entire board is that Carvin's own website, https://carvinaudio.com/pages/bass-amp-schematics shows different versions of the B2000 schematic but none of them matches what I see in the version I'm trying to troubleshoot. There is one vacuum tube in the unit, a 12AX7.   After cutting out the MOV, and then powering it up, the power relays would not engage. The other issue is that when I pulled out one of the two power relays for inspection of its discolored contacts after it failed to power up, one of the pins came out of its coil. There is no writing on the relay and its physical construction doesn't look at all familiar to any relays I've ever seen. I need to replace it assuming the unit is worth fixing.   Does anyone have a schematic for this amp? There is a description of the amp here: https://carvinaudio.com/pages/archive-carvin-b2000-lightweight-mono-block-2050w-bass-amp-head   The owner said it was purchased around 2000. It looks in good shape for being 20 years old. According to this report, https://www.thetonerooms.com/threads/carvin-amps-out-of-business.3035/ Carvin went of business in 2017.   Thanks for your replies. -- David Farber Los Osos, CA

Phil Allison <pallison49@gmail.com>: Sep 20 08:06PM -0700 David Farber wrote:   =================== > being 20 years old. According to this report, > https://www.thetonerooms.com/threads/carvin-amps-out-of-business.3035/ > Carvin went of business in 2017.   ** No schem from me- but it looks like you may only have a bad relay.   The blown device is a PTC thermistor not a MOV - they are fitted to reduce excessive inrush surges at switch on. The relay bridges the PTC out of circuit to stop it overheating and exploding if made to pass the full load current.   You can try using a 5 to 10 ohms, 5 watt or more WW resistor in place as a test and then bring the amp up with a Variac.   If the resistor smokes, you have a blown PSU.     .... Phil

David Farber <farberbear.unspam@aol.com>: Sep 20 10:17PM -0700 On 9/20/2020 8:06 PM, Phil Allison wrote:   Hi Phil. I think I'll try using one of my audio, 8 ohm, 25 watt dummy load resistors to test it. I'll also put a 200 watt light bulb in series with the Variac just in case. If there's no overload, then I may as well pull out the other identical inrush relay and see if I can figure out what voltage and current it takes to close the contacts. Any idea what voltage and current rating those contacts need to be?   Thanks for your reply. -- David Farber Los Osos, CA

Phil Allison <pallison49@gmail.com>: Sep 20 10:40PM -0700 David Farber wrote:   ==================     > Hi Phil. I think I'll try using one of my audio, 8 ohm, 25 watt dummy > load resistors to test it. I'll also put a 200 watt light bulb in series > with the Variac just in case.   ** That's fine.   > If there's no overload, then I may as well > pull out the other identical inrush relay   * Are there 2 PSUs involved?     > and see if I can figure out > what voltage and current it takes to close the contacts. Any idea what > voltage and current rating those contacts need to be?   ** 20A at 120VAC at least.     .... Phil

legg <legg@nospam.magma.ca>: Sep 21 09:46AM -0400 On Sun, 20 Sep 2020 22:17:29 -0700, David Farber >pull out the other identical inrush relay and see if I can figure out >what voltage and current it takes to close the contacts. Any idea what >voltage and current rating those contacts need to be?   It's a fairly common form used in HVAC switching, but more easily obtained with a plastic dust cap. The open air parts are seldom used outside of self enclosed fan-free environments, for obvious reasons.   You may have a relay on both input (inrush limiting) and output (click and pop supression).   You'll need to establish what the supply voltage is for the coils.   Check for Panasonic JTV or TEconnect T9AS1D series SPST NO.   RL

legg <legg@nospam.magma.ca>: Sep 21 09:59AM -0400 On Sun, 20 Sep 2020 22:17:29 -0700, David Farber <farberbear.unspam@aol.com> wrote:   Actuslly, the second relay looks more like a line voltage selector. It will close for line voltages below 180VAC.   It looks like this unit isn't power factor corrected.   RL

legg <legg@nospam.magma.ca>: Sep 21 11:34AM -0400 >Actuslly, the second relay looks more like a line voltage >selector. It will close for line voltages below 180VAC.   >It looks like this unit isn't power factor corrected.   If that's the case, then you could do a quick fix by relocating the voltage select relay to the inrush position, short out the old voltage select relay contact position, then place a large sticker on the back indicating "100-130VAC INPUT ONLY".   RL

Tom Kupp <tjkupp@gmail.com>: Sep 22 10:22AM -0400 On 09/18/20 11:53, danny burstein wrote: > a magnifying glass and hold the unit at an angle > to the light, that you'll see, in teensy raised > print, the numbers you're looking for.   No joy, just says POWER.

Fox's Mercantile <jdangus@att.net>: Sep 21 10:09AM -0500 On 9/22/20 9:22 AM, Tom Kupp wrote:   > No joy, just says POWER.   Look inside and and follow the power from the connector. First, the center pin should go to the supply bits, not to ground. That shows the center pin is + or -.   Then see what they're using for a regulator. The input will have to be more than that.   Does it have a bridge rectifier? If so the supply was probably AC, but you can use a DC supply with it.   Lastly, first try a +5 v supply, if that doesn't work, then try a +12 v supply.     -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

"pfjw@aol.com" <peterwieck33@gmail.com>: Sep 21 08:19AM -0700 https://www.cnet.com/products/cn5614xr-fax-modem/   The internet is your friend. You might also try contacting CNet.   Peter Wieck Melrose Park, PA

Bo-Lennart <bo-lennart.karlsson@telia.com>: Sep 21 05:23AM -0700 Hi.... I still looking for a service manual för either B&K FET-VOM 179 or KYORITSU FET-VOM K-200. I would like to adjust the instrument in a proper way. I have found some schematic on the net. And it seems that there are at least 2 version of that instrument.   Best regards from SWEDEN Bo-Lennart Karlsson bo-lennart.karlsson@telia.com

Fox's Mercantile <jdangus@att.net>: Sep 21 09:20AM -0500 On 9/21/20 7:23 AM, Bo-Lennart wrote: > I still looking for a service manual för either B&K FET-VOM 179   Have you tried the B&K website? They claim to have manuals for everything they ever made.   -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

Peabody <waybackNO584SPAM44@yahoo.com>: Sep 20 03:54PM -0500 > to replace (except you'll have to identify them, and > match to modern available parts, and pay shipping for > onesies...).   I removed all of the electrolytics, and all but one tested good on my scope. I replaced the dubious one, but the flash still doesn't work. The oscillator whine doesn't start up.   But I did find one thing that gets really hot when the power switch is turned on. It is a pair of three-pin parts (triange pattern footprint) that look like cylinders, and they are enclsed in a U-shaped heatsink. They are each marked with the Mitsubishi triagle logo, and "B324ST", with "12" on the second line. I assume they are transistors or thyristors, but searching for them comes up with nothing. This is all from the 1980s, so I guess it's not surprising that the parts aren't active anymore, but it would be nice to at least find a datasheet.   By the way, the dubious cap was right next to the mystery pair.   Any ideas?   https://www.eevblog.com/forum/repair/repair-vivitar-3500-speedlight/? action=dlattach;attach=1070818;image

Peabody <waybackNO584SPAM44@yahoo.com>: Sep 20 04:06PM -0500 Someone on the EEVblog forum says the part number is actually 2SB324, which is a germanium PNP transistor. I'd guess I won't find a direct replacement for that.

"dansabr...@yahoo.com" <dansabrservices@yahoo.com>: Sep 21 04:18AM -0700 On Sunday, 20 September 2020 at 17:06:12 UTC-4, Peabody wrote: > Someone on the EEVblog forum says the part number is actually 2SB324, which > is a germanium PNP transistor. I'd guess I won't find a direct replacement > for that. If you need 2SB324 transistors, I have them in stock. They don't have the heatsink attached, but I have heat sinks as well. Send me a private message so we can connect.   Dan

Phil Allison <pallison49@gmail.com>: Sep 20 08:13PM -0700 Hi,   a Fender Princeton amp came to me with its reverb making bad noises at the slightest bump or movement of the amp. Bit like an elephant walking on piles of sheet metal.   When I removed it from the back of the amp and opened it up, I saw what the problem was in a second.   see link for pic of a MOD reverb tank.   https://surfguitar101.com/forums/topic/30892/?page=1#p415794   Note the piece of foam supporting the two springs in the middle. No kidding, it was still there.     ..... Phil

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