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Cydrome Leader <presence@MUNGEpanix.com>: Oct 14 03:53PM > I've no r/c with this machine. No response to open/close button. > Anyone come across a machine where you cannot use simple front buttons , > although physically present and wired up.   Well, sony had some commercial VCRs with a key inhibit switch that locked out most of the front panel. Obviously not related to your problem though.

capossio.leonardo@gmail.com: Oct 14 08:18AM -0700 Hello,   I was wondering if you could help repair a guitar amplifier, it is a Fender Frontman 212R, schematics are here: http://support.fender.com/schematics/guitar_amplifiers/FM212R_schematic.pdf   The problems are: -Low volume. It is a 100W amplifier and at full power is delivering something like 20W tops at max volume. -Paper crackling sound when guitar is played very hard. It is very subtle, but is annoying.   I know that: -Power supply voltages are ok (including the power amp stage) -Speakers are ok (it has two speakers of 8 ohms in parallel as load) -Nothing seems to be burnt on the PCB, or any cap seems bloated or something   It is unknown to me what the PTC (RT2) is doing, I know the NTC (RT1) is for mains thermal shutdown, but the PTC seems to be for thermal shutdown of the power stage only (because it is thermally coupled to the power transistors power dissipator with some paste).   The next time I see it I will try to see if it is a pre-amp problem or a power amp problem (because fortunately it has a pre-amp out and pwr amp in)   Thanks.

N_Cook <diverse@tcp.co.uk>: Oct 14 04:27PM +0100 > a power amp problem (because fortunately it has a pre-amp out and pwr > amp in)   > Thanks.   Is there a send/return pair, that you can put a test signal in the RET to narrow to PA or PREA. Suddenly happen or previous intermittant level change?

Leonardo Capossio <capossio.leonardo@gmail.com>: Oct 14 08:51AM -0700 El miércoles, 14 de octubre de 2015, 12:28:01 (UTC-3), N_Cook escribió:   > Is there a send/return pair, that you can put a test signal in the RET > to narrow to PA or PREA. > Suddenly happen or previous intermittant level change?   I don't have a signal generator, at least not now. I will put the pre amp out to another guitar amplifier that is working 100% and see what happens. If this works with a good sound I think it safe to say that the problem is not in the pre-amp.   The crackling sound seems to appear when strongly strumming the guitar. The volume does not go up or down, it just never reaches a level above lets say 20W.

"pfjw@aol.com" <pfjw@aol.com>: Oct 14 07:06AM -0700 On Sunday, October 11, 2015 at 12:45:31 AM UTC-4, veek wrote: > being very loud. So is my assumption correct?   > Are there any modern features I could look for in an amp. My TV is a > Samsung 4003 720p and it has Component Ports for audio/video.   OK - a few basics on speakers - at least as they were sold in the US under FTC regulations (sit on your fingers, Phil!):   a) Rated power is based on CONTINUOUS power into the speaker. So, a "20-watt" speaker should be designed to accept 20 watts of continuous power at some mix of frequencies, usually specified, for some specific period of time, also usually specified.   b) Rated Power is not Average Power. Assuming a speaker that produces 90dB of noise at 1 watt at one meter on-axis. Assume a normal peak-to-average of 20dB on the incoming signal, and assume it is running at one watt average (quite loud). Then the speaker will be getting momentary peaks of up to 100 watts (assuming the amp is capable of such). This will do NO damage to the speakers whatsoever as-described.   c) Low cost, low-wattage amplifiers are much more likely to cause speaker damage than large amplifiers. What can happen with some solid-state designs is that when the amplifier clips (called to produce more power than it can), it may send straight DC into the speaker - which will destroy voice coils in short order. So, the larger the amp, the less this may be an issue. As one example, I run 30-watt rated speakers with a 200-watt-per-channel amp, and have done so for years with no issues at all.   So, unless you wish to listen at ear-bleeding volume with an audio-quality source with full-orchestral signal (none of which are likely from a computer source), 30 watts is far more than enough. Another exampleL I run 86dB speakers from a 60 watt-per-channel amp at moderate levels, no problems and no clipping. The speakers are rated at 100 watts, as it happens. The key is *moderate levels*.   This issue is far less so from a tube amp - the simplistic explanation is that it is harder for a transformer to pass DC, so tube amps clip softly. There is much more too it, but for this situation, that is enough.   Peter Wieck Melrose Park, PA

N_Cook <diverse@tcp.co.uk>: Oct 14 08:20AM +0100 On 11/10/2015 18:34, Madness wrote:   > The dental probe sounds like a good idea. Might get better access if I > remove the front panel. Incidentally, if I turn the deck on its side & > play a tape, there's no flutter.   Attitude effect suggests a bearing problem. Assuming sintred metal bearing , you can sometimes get a bit more life from the following. Squash the bearing between 2 tiny ball bearings , set in a pair of nuts or something, squashed in a vice. Matter of suck-it-and-see. Try low force initially and try out with the capstan and repeat with gradually increasing vice force

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