jeffs
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Everything posted by jeffs
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Transistors don't typically show that much physical damage. Looking at the schematic, the best case scenario for you is that C29 shorted, causing excessive current thru the diode and transistor. I noticed C29 is removed in one pic. If it measures shorted, it's likely the cause of the damage. The resistors in that circuit can get hot. Their proximity to the 1000uF caps can shorten the life of the caps. I would recommend replacing the 1000uF caps in that circuit, and mounting the replacements on the back of the board. Can alleviate future potential thermal problems with these caps.
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You get to demo the speakers of your dreams with ONE track…
jeffs replied to Daddyjt's topic in Favorite songs to X by
I don't listen to CDs often, but Love Over Gold pretty much has a permanent spot in my home office 5 disc changer. -
You get to demo the speakers of your dreams with ONE track…
jeffs replied to Daddyjt's topic in Favorite songs to X by
Interesting. With the other songs on that recording, I could never have guessed that would be the pick. I don't have a simple answer to this question. Some days I might pick "Dreams" by Fleetwood Mac, off the DVD Audio disc. On a more acoustic feeling type of day it could be "Trouble's What You're In" off Wheels Turn Beneath my Feet, by Fink, ....or "Keith Don't Go" by Nils Lofgren, acoustic live version. Most days it would be something by Dire Straits. "Private Investigations" is a good one .... maybe "You and your Friend" If I had to choose a vinyl recording it would be something off Dire Straits self titled album, probably "Six Blade Knife" or "In the Gallery" -
New to Site with MXR-2000 issue
jeffs replied to markdd's topic in The Welcome Shop (Please read first)
I replied to this 3 days ago as it was posted in the main area as well: -
Tidal certainly looks like the best option for Tesla. You would need the Tesla Premium Connectivity option which I think is free for a while, then $100 for an annual fee (or $10 a month). If you don't use Premium Connectivity for anything else, then you have to factor that in. I wanted to like Qobuz. I mean I really wanted to like it. Problem is that it's limited to phones, computers, and maybe some high-end streamers. There are no apps for Firestick, Roku, or Apple TV streamers. "Casting" is not a very good solution. I tried that with intermittent results and constant frustration. Amazon Music streams in HD on computers and Firestick streamers, reduced resolution on the other streamers. Doesn't answer your question directly, just my experience with some of the high resolution services.
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The 901s and m1.5t is a good combo. I had it for a while and it can go big ......... problem is the 901s are not very good at lower levels (just my opinion). The front plastic bezel on the m500 can be polished with a succession of Novus 1/2/3 polish, from coarsest to finest, depending on the level of damage. There's probably a thread if you do a search
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If you look at the service manual, the bulb looks replaceable. Item 53 in this diagram The schematic is not all that easy to read, but it looks like it's a 10V bulb? It's supplied by the top of the 3 regulators shown below. First step would be to find this lamp and put a voltmeter across the 2 terminals to make sure you have 10V. 99% likelihood it's the lamp, but make sure. Could be a shorted cap on the output of the regulator, or a bad regulator. Never seen one of these so take it apart, out if you can, take a pic and post it.
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you might need cap head screws (hex drive)? The heads are smaller in diameter. I've made this work in the past but no longer have that setup. My custom rack rails inside is 17 7/8".
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I assume both pieces have the factory notched faces. Reply is based on that. I've made my own racks and have a bit of control over width. I've used Sanus racks that had a bit of adjustability in the width. I could get clearance in those situations. Can you angle it in on one side and rotate to get clearance Clarence? .... or are the screws right where the rails are so you can't get past them? A pic would be great but I know you don't have those privileges yet ....
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The spring action is fine. They have a decent amount of throw before they latch. You really need elf fingers as the button itself is quite small. Resting fingers on the top of the unit and pressing with a thumb tip works fine. I detailed this in a different thread, but don't remember where. I basically copied the C-1 gain stage which includes balance. It's easier to show using the C-19 schematic - which is more-or-less the same: So - here's the issue with this, while you do need only a single pot (3 connections) for balance, it's less than ideal. In the default state, with the 50K pot shown, it basically puts 25K ohm in parallel with each volume pot. Not really much of an issue. When the pot is turned all the way to one side, it puts 50K in parallel with one sides volume pot, and ZERO ohms in parallel with the other side. So - you see the 820ohm resistor? It serves as the minimum load that the previous stage will see with the pot twisted all the way. Without it, the previous stage is presented with a ZERO ohm load. In the case of the C-19 shown, the previous stage is an internal op-amp, followed by 1K ohm, so that op-amp would be presented a 1.82Kohm load. Not really an issue. In the case of the C-1, I think the 820 ohm is the same but the 1K changes to 1.5K, so the presented load with balance turned all-the-way would be 2.32Kohm..... however, there is no internal op-amp, so this low load is presented to whatever is connected to the preamp input. It's less than ideal, but is it a problem? It's hard to say but I've never had an issue using a C-1 preamp and I like them quite a bit. I've also never run a unit with balance turned all the way to one side. I will say that once I gave this some thought, I chose to NOT use the balance connections on 2 of the units I built, it's only on one. In the case of my manual unit, I used a C-1 20K ohm takeout 2-gang volume pot. In the case of the remote volume units, the volume pots are 50Kohm 2-gang motorized.
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Top: simple 2 channel preamp with SH. Volume and SH functions remote controllable. Middle: simple 2 channel preamp with SH. Manual volume and SH switching. Bottom: SH only. SH switching via remote control. Input1, Input switch, Input 2, Preamp out, line level out. One unit has balance control under the input switch. Almost 200 mounted components, all surface mount except electrolytics. Tedious work but at least my hand is still stable enough to do it. This was my winter project. Mostly for fun and to keep up on a few skills.
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My point was that there were NO Topping amps on your linked list. As far as my "vote" goes, don't twist my post to fit your poll. You clearly did not read my reply in its entirety. I've probably owned more Carver vintage amps and preamps than anyone on this site. My list includes 58 amplifiers. I don't count preamps, but I'd guess it's between 20-25. It would be interesting if anyone could top these numbers. Granted - some of these were flips, but none of them were consigned repairs. I purchased, repaired, tested and listened to every one of them. I'm often asked to repair/refurbish other peoples gear and I politely decline. It's not what I do. I currently own 7 amps and 2 preamps, plus a few units that I have gifted to my adult children. I expect these numbers to stay static as I'm not interested in acquiring more gear. There are always exceptions. I've owned ZERO amps of any other make since 2014 or so. I was gifted a vintage Denon integrated which I never intended on keeping and sold after repair. I don't count that one. These are facts. I'm not sure how you equate this to me preferring cheap gear that tests great.
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I'm confused as to what point you are trying to make here? Your question is in regards to audio amplifiers? Correct? I followed the link that you provided. I reviewed the "categories" of the items listed. Only ONE listing was for an "Amplifier". No price is shown as this is a "Wanted" listing! All of the other "Topping" listings are for items such as DACs, preamps, Headphone Amps, etc. Fact is, people buy stuff and no longer have a use for it, for a variety of reasons. The result of only 30 listings of Topping products across the board actually seems quite low to me, based on what I would guess is a very high sales volume. If you turn your search to "Carver" you will find At least as many listings for gear. By your logic, Carver gear must be no good since customers are "parting ways" ........ I thoroughly enjoy most of my Carver gear of the 80s. I occasionally replace a unit which means I have one to sell. Does not mean that I didn't appreciate it, just that I no longer need it. I think Topping makes very good DACs at reasonable prices. I have no knowledge of their other products. A while back I was using a low-end Schitt DAC on my desk/bench. It sounded decent, but the digital noise from the computer USB was beyond noticeable. I also had a low-end Topping DAC available .... sounded great, had more features, and was dead quiet. I couldn't sell the Schiit fast enough. The opinion was based solely on my personal experience. I have never bought or sold a product based on a review on ASR ... or anywhere (actually I once bought a pair of speakers based on reviews .... mistake). Just my opinion: In todays economy, people's discretionary spending dollars are limited, probably more so than in the past 15 years, maybe longer. Personally, I've cut way back. Every purchase of this type is going to be thoughtfully considered. Table of Topping gear categories as listed on USAM, per your link:
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Questions for Bob Carver. Ask here.
jeffs replied to Ar9Jim's topic in Bob Carver Corp Today.'s BCC Tech Thoughts From Jim
If you use a C-1 in it's simplest form using a line input with no switches engaged, that's pretty much what you get ..... except ..... The problem with this circuit is the way balance is implemented. It's really less than ideal. If you leave tone control out, the input is essentially connected to the left side of R335. The preamp input impedance becomes R335+R336+ (20K volume in parallel with 25k( 1/2 of the balance pot)= 13.42K. Already somewhat low but acceptable. If you turn the balance pot all the way to one side, the volume pot is shorted to GND on the other side. The input impedance on the opposite side becomes R335+R336= 2.32K .... So the input impedance is dependent on balance pot position. Otherwise the C-1 simplest path is more-or-less just a volume pot followed by a simple gain circuit (18.6dB). -
Welcome. The PM100 and PM300 are indeed the same amplifier. I've never owned a 300. It might have a different main pc board? No upgrades that I know of. I believe the PM100 shares a main PC board with the m200t? They do have different output transistors. I do remember a m200t upgrade thread. I think the general conclusion was that it didn't add much. Not sure how applicable it would be. The 1U height of the PM100/300 is going to make modifications challenging.
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PC board quality has come a long way. You have to try really hard to get low quality boards these days. Even low-cost boards from the hi-end Chinese houses are very good. You can dial in everything - pay as you go. Copper weight, layer thickness, board material, etc. 20-25 years ago if you went low end - it was pretty bad. Not going to name names, but some of the Carver amps built in the first 1/2 of the 90s have very poor quality PC boards. Corners were cut in that timeframe.
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New member looking for light
jeffs replied to Dorian's topic in The Welcome Shop (Please read first)
I would agree. It's probably the worst amp to start your Carver repair journey. One bright spot is that the amps are mostly completely independent channels, including power. If one channel works, you have a reasonable reference. It's not a commonly discussed amp so I would not think there are any threads regarding repair. I fixed a PT1800 a long time ago ... have stayed away from these amps since. The PC boards are dual sided. For me, this significantly adds to the repair challenge. -
If the DC is high yet reasonable (under 60mV or so), check the input AC coupling capacitors for shorts. Many models this is 470uF, but others have 220uF. For which model? The m1.5t does not have a thump fix bulletin. It's one of only a few models (m400 series) that does not have a power switch. It's "instant on" as soon as it's plugged in.
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welcome!
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I ripped most of my CDs onto a Mac years ago. At that time, no special software was required, ripping was part of the "iTunes" application. My 2010 Mac also had an optical drive. Most (all?) Macs have not had an optical drive for many years .... maybe you have an external one? Additionally, iTunes is a thing of the past, but I would think the Apple Music app has ripping capability? Apple Music has fully replaced iTunes.
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I understand this statement completely. Strongly agree, I have the same proclivities. The pictures of your work tell me all I need to know. I enjoy it as well. I'm just tinkering right now. After adding the preamp/volume to my C-9, I was very satisfied .... but I wanted more. I wanted to be able to remote control the switching. It's something that's certainly do-able in the current C-9. After some thought, I realized that it was the wrong approach. Why not just keep the electrical design but redo the mechanics? I needed a project ..... keeps the brain from turning to sawdust. Like I said ... just tinkering. Still have yet to pull the trigger on it. I'm really looking forward to the new SH implementation from Bob. One of those will be in my rack.
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A new SH stand-alone product should be 95% surface mount components. It's 2023. Building surface mount in volumes is the way to go. Not sure how the tube buffer would fit in as I know jack about what that circuit needs to look like. I actually have a layout for a surface mount C-9. Hope to make it fully remote controllable. It's a 4x4in pc board. Includes the power supply and 2 input preamp. Only the power supply caps and the 22uF coupling caps are thru-hole. Remote receiver is a separate board, transformer is separate. I was bored a few weeks back and it was raining so I laid it out in a day or so.... tweaked it here and there. Mostly did it for fun and to kill a few hours. I'm really curious if adding a ground plane quiets the annoying hiss when SH is enabled. This might just be a by-product of the comb filters, but I'm still curious. I have yet to pull the trigger on the boards. Building this by hand with mostly 0603 SMD components will be a huge challenge. I've built a number of surface mount boards by hand, but the component count was much less than what would be required for this project.
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While I guess it's important for a unit like this to share styling with the other products, it will be purchased by people who have no intention of purchasing the amp or preamp. I'd guess this was the same story for the original C-9? Many were sold to people who did not buy Carver preamps? Like the C-9 it should fit in a 1U rack space. Rack mount ears would be a simple option, no need for a dedicated rack mount face. Tubes seem completely unnecessary, and meters on a pre-amp make no sense and will only drive up costs. Make it simple. The suggested switching options sound good.