- Antennae Booster - 1 Update
- Carvin B2000 bass amp won't power on, need schematic. - 3 Updates
| Mike S <mscir@yahoo.com>: Oct 04 01:54AM -0700 On 9/23/2020 3:06 AM, Pimpom wrote: > an aluminium coat hanger plugged into the antenna socket. By contrast, I > could watch the 1990 FIFA World Cup only with an array of four yagis > *and* an antenna booster. Is it possible there was construction going on somewhere between the source antenna and your work? |
| David Farber <farberbear.unspam@aol.com>: Oct 03 02:49PM -0700 On 10/1/2020 11:51 PM, Phil Allison wrote: > Those are high power IGBTs and they do not blow without a reason. > ..... Phil Thank you Phil and RL. After much poking and prodding trying to reverse engineer which circuit was going where, the previous 105 ohm low readings across D809 and D810 are now normal. Maybe a spec of solder took up residence in the area when I was desoldering the adjacent transistors, Q800 and Q802? Next (but still without a new set of IGBT's installed) I slowly powered the unit on with the Variac. Relay K1 now energizes right after power up and the internal green LED glows normally. I will now place an order for the IGBT's and NTC thermistor. Phil brought up the point, what would cause them to blow in the first place? After much checking, I could not find any other faults in the circuitry. I'll update you after the new parts arrive and are installed. I do have one other question regarding the 25A line fuse. What the heck is that supposed to protect? If the power supply fails/shorts, the thermistor bypass relay de-energizes and then the line voltage is sent through the thermistor. I think the 25A fuse will win that battle and not protect anything. The specs on the back of the amp say, 2050W into 2 ohms so I guess a large fuse is necessary however wouldn't a smaller fuse, maybe a slo-blo type, make more sense? One last comment about the schematic. This B2000 model is a mono amp so anything in the schematic that says CH2, does not exist though about one-third of the circuit board has empty spots for those components. Thanks for your replies. -- David Farber Los Osos, CA |
| Phil Allison <pallison49@gmail.com>: Oct 03 04:33PM -0700 David Farber wrote: ------------------ > cause them to blow in the first place? After much checking, I could not > find any other faults in the circuitry. I'll update you after the new > parts arrive and are installed. ** I have you have an isolation transformer or a scope that can be safety floated above earth. You need to inspect the drive waves to each IGBT. As you Variac up, the wave should snap on staring with a very low duty cycle, then fill out to a perfectly symmetrical square wave. > not protect anything. The specs on the back of the amp say, 2050W into 2 > ohms so I guess a large fuse is necessary however wouldn't a smaller > fuse, maybe a slo-blo type, make more sense? ** At full power with 2ohms load, the AC will be 25amps RMS. ( 2100 /120 = 17.5 with a PF of about 0.7 = 25. ) If you know the speaker being used is 4 or 8 ohms and the player does not thrash the heck out of it - then a 15amp slo-blo will do OK. .... Phil |
| David Farber <farberbear.unspam@aol.com>: Oct 03 10:27PM -0700 On 10/3/2020 4:33 PM, Phil Allison wrote: > ( 2100 /120 = 17.5 with a PF of about 0.7 = 25. ) > If you know the speaker being used is 4 or 8 ohms and the player does not thrash the heck out of it - then a 15amp slo-blo will do OK. > .... Phil Thanks for the tips. I'll check out the drive to each IGBT while powering it up slowly. -- David Farber Los Osos, CA |
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