MikeS

Here's a ad I pinched from a May/June 1991 issue of Car Stereo Review. Looks like a pro sound driver.......pleated cloth surround, treated paper cone, and probably a four inch voice coil I would guess. They pretty much say it's a pro sound driver....

Is that just a record player with a amplifier, or does it have AM/FM radio as well? Unless you have parts on hand to try to troubleshoot and replace the parts needing replacement, I wouldn't spend money on it. Could be any number of reasons why it sounds bad. Anything from a toasted cartridge, (like Jim mentioned) to bad resistors, dried out electrolytic capacitors, or maybe bad pre-driver or driver transistors. The circuit could need to be re-biased, which would be either through a trimpot, or a resistor......I'm betting the latter. The little low voltage 'lytic capacitors can and will dry out over time, especially if the unit is over 30 years old. Which makes me ask.......How old do you think that Zenith record player is? You say it's all point to point wired........It doesn't have any printed circuit boards at all? A schematic is a real nice option when tracing and troubleshooting a unit such as this. For what's worth, I'd just see if that older lady would rather just scrounge up a cheap vintage turntable and a vintage integrated amp or receiver with a phono input. It isn't worth pouring time and money into that Zenith record player, unless she holds some sort of sentimental value towards it.

No Todd, I never did get the Eico ST-70 to work properly. The very first time it did work, but I had the 6SN7's connected wrong which yielded literally no gain and real distorted output. Then when I did connect the 6SN7's right, I ended up with a major midband oscillator. I rebuilt the amplifier, with some mods sourced off the internet. I thought maybe the modifications were contributing to the amp going into positive feedback, and then converted the amplifier into a straight power amp hoping the positive feedback issue would go away. It didn't...... I used speakers for load, and it would really scream with positive feedback. I had a couple guinea pigs at the time in the room. It would put them into serious launch mode......one would shoot a foot straight up, and then do about 30 laps in it's cage within 2 milliseconds......they hated it.......so do I........I need to buy some load resistors from PE. If the Altec amplifier turns out to be a stable circuit, and I don't end up troubleshooting the thing, I can go ahead and return back to the Eico ST-70 and start troublshooting that amp. I need the load resistors for both amplifiers to do proper bench testing troubleshooting. I got the scope, the probes, the half-assed signal generator......I just need the load resistors..... I need to chase out what section of the circuit is causing/going into positive feedback, using a scope will help. It could be a bad capacitor can, a scope will help chase that out. And I'm the learning curve when it comes to bench testing amplifiers/troubleshooting.....I'll finger it out..... I still need to buy the R's and trimpots, but I'm getting pretty close to having this Altec amp finished.

Radio Controlled top fuel?

How strong is your back? http://www.atlassound.com/Product.aspx?id=571 Technical Specifications Power Handling: 250 watts (45V) RMS Sensitivity (1W / 1M): 102.5 dB SPL (75 Hz

No doubt......wotta buncha ol' grannies.... Just get a couple of these and strap them to your back. http://www.atlassound.com/Product.aspx?id=564 Power Rating: 15 Watts continuous Frequency Response: 400-4,000 Hz Sensitivity: 102dB at 15 watts, 10ft (3dB increment UL Rating) SPECIFICATIONS (ANECHOIC MEASUREMENTS) Frequency Response: 400-14,000 Hz (Nominal) 500 - 6,000 Hz (

They are out there....they just probably cost a lot of money..... Nebraska Surplus might by another online site for high power load resistors. http://www.resistorsonline.com/wire-grid-resistors.html I'm not sure if the OP (SS) wants to use the scope connected to a speaker(reactive load) to monitor/tweak system response, or if he wants to measure a amplifier for bandwidth/power output.

You should get some sort of owners/operating manual with the unit if you had bought it new. It should explain the basics of scope operation with regard to the model of the oscilloscope. Tektronix has scope primers on the website. Most amplifiers are measured with a resistive load on the bench with respect to bandwidth/power output into a scope from what I understand. The power output of the amp and the impedance at the output, will determine what size wattage and ohm rating of the load resistor/resistors. The load the amplifier sees will vary when the input signal is changed over the audio band with a reactive load such as a speaker.....sumthin' like that.... The lead with the alligator clip is probably the ground.

I messed up the link to the last photo....

Heaters are done. B+ for the OPT's is almost done. I'm working the screen de-coupling circuit as well. Then the B+/de-coupling/filtering sections for 6C4 and 6AU6. I can then start pondering and wiring out the negative bias circuit. (still need them 5K trimpots and 10 ohm R's) From there, I can probably go ahead and wire up the coupling/DC blocking caps and the rest of the signal circuit, and then wire in the input signal leads and the volume pots. I also still need to hook up the power supply grounds, and signal grounds as well. And then wire in the power cord and power switch. I still need to drill some holes and mount binding posts and the back panel. That's all I can think of at the moment..... I won't take too long now that I'm actually wiring and laying the circuit out.........but I am slow....

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Don't see why you couldn't......as long as the plate amp can cool itself. Like Jim says, find a integrated amp/receiver be it vintage or whatever for front and right stereo, and a plate amp for the subwoofer. You may find out the setup will sound much better, especially if the plate has a variable internal xover or whatever, to blend the subwoofer with stereo L/R speakers. I run a stereo 1/4" jack to RCA jacks right out of the PC into a old JVC 60 watt integrated amplifier. I think my PC has a sub LF out, but I don't worry about it much.

If the receiver has a blown side, the unit is probably borderline unstable. The high pitch you hear is probably a mid to high band oscillation. The popping could be bad cap or more, decoupling when they shouldn't be....maybe.... You have blown output transistors on one side, with no doubt probably damage to the pre-driver/driver stages. It probably won't be long until the other side dies.....

So you are saying that folks who hear differences in various amplifier topologies, have either bad hearing or not very smart?

Dunno what's wrong with photobucket............... I didn't unwind the xformers, I just pulled the end caps to inspect them and repair the insulation damage to the PS heater windings. My old retired EE buddy has unwound, gapped and done interesting things with transformers, but it's way beyond my scope and capability. I'd end up with a pile of scrap copper/iron and paper. I got a Radio Designers handbook that explains how to wind xformers and theory/math, etc......but it is real deep for my peanut brain without learning some math. OPT2 OPT The first one appears to be discolored from heat stress. But I don't think it is. The OPT's are not consecutive in the part numbers. One may have been from a different run. You can see how the wax had gotten hot. PS Heater winding insulation damage.

Yeah, the transformers were kind of a pain in the ass. But they are Peerless. Peerless was a well respected transformer company in the tube heyday, especially when it came to audio related products. Well engineered. Look at this way......a retired EE who is around 72-73, and a audio buff for 50 years, mentioned that the amp is probably a keeper once he knew it had Peerless OPT's. A local retired audio engineer who is in his 60's, asked if the amp had Peerless iron. And then got a grin on his face when I said it did. The specs in the operating instructions claim 40 watts RMS continuous each channel at less the 1/2% THD @ 40-15kHz. 100 watts peak per channel. Even at 40 wpc RMS, I still think that's crowding the amp kinda hard......who knows, it's 1959 measurements. I doubt I'll listen to more than 20 watts per side without getting blasted...more like 10.... Frequency response + or - 1db, 10Hz-100kHz. It takes a rather tightly coupled, (wound) output transformer with a good size core to get those numbers. I have no idea what wattage those measurements were made at. I'm working on the amp now. I have all the parts, except four 5k trimpots, and four 10 ohm 5 watt current sensing resistors.

If this place hadn't went tits up years ago, I could just take it down there and complain........

Yeah, the PS transformer has a 1/4" diameter by 1/8" deep hole drilled in the lamination stack on the bottom. This was from a repair job. The amp had undergone some thermal stress at one time, and I don't know how or why. It cooked the 250 ohm dropping resistor for the screens of EL-34, going ablaze. It wiped out the insulation on the 5 volt heaters for the rectifier tubes, and part of the 6.3 volt winding for the signal and output tubes. The repair was to fix the burnt resistor. The imbecile broke out the black and decker with the 1/4" bit to drill out the tag strip that the resistor was mounted to,(underneath the PS xformer)and power rammed it through the chassis and into the lamination stack. Then he mounted a new tag strip and resistor between the rectifier tubes, drilling another hole in the chassis. I tore the PS xformer down. It did undergo a bit of stress, with some wax melted, but not too bad. I then removed the burnt insulation on the heater leads, and replaced the insulation. Once assembled, I measured for DCR, and then measured AC with the xformer unloaded. DCR #'s for the PS xformer are right in spec with the Sams photofacts for Altec 345A. (I never really trust sams phonyfacts, but it did make me feel a bit more confident.) AC voltage unloaded on the secondary is a bit higher, but it's for 117 volts in. Where I was measuring at 120 volts in. That's my wall voltage, so I gotta go from that. I then ran the PS xformer for around 7-8 hours unloaded. 120 volts AC, with the secondary and heater leads taped-off, floating. A wore out power supply xformer running unloaded with say a few shorted windings will heat up. Some may start to buzz, even more so if the input voltage is exceeded a bit. But this Peerless xformer is big beast, and probably rated pretty well and would take a bit more abuse. After 7-8 hours, it got mildly warm unloaded.....I'll see how it does with a load. The only other PS xformer I have that is larger, is a Masco 6550 PP PA amp. The PS xformer is a big ol' 20-25 pound monster. Even the big old tube television PS xformer's don't even come close. One output transformer was in good shape, the other had got rather hot at one time. Hot enough to shift the lamination stack crooked. I disassembled both OPT's, one looked fine. The other I took to work and heated the OPT in a electric oven. Once warm enough, I re-aligned the lamination stack straight. It worked well, and the whole place reeked like wax...heh I put them back together and measured the DCR numbers, they are still close enough. They won't be exact I suppose. I measured both OPT's with a sig gen using square waves with a simulated load for the primary, and a dummy load for the 8 ohm secondary tap. Shorted windings would show peaks and quick drops in the square wave response around midband. I didn't see it, and response between the two was quite similiar. I bought it from some old timer in his '90's. He's the first owner. I doubt he had turned this amp on in 30 years or better. Who knows.......but it was a den and a latrine for a mouse for quite some time, the chassis was trashed. It was a real basket case to be honest.

Peerless. It's a Altec Lansing 345A stereo power amplifier. Roughly 1959 vintage? http://www.hifilit.com/hifilit/Altec/1959-d.jpg I haven't used a tube active linestage in quite some time. Mostly due to time factor, I've been using a vintage SS Harmon Kardon 330B receiver. When I do listen to a tube amp, I've used the digital volume control in the remote of a mid-tier Pioneer CDP. While it doesn't fully attenuate the signal, it lowers it enough to feed direct to the amplifier. Pretty much noise free simple path......but the Pioneer is getting long in the tooth and starting to sound wretched....I may give it some TLC..... So the other day I went to RS and bought all the 100K stereo pots they had. Out of three I lucked out on one, where it's within 1.5% of each side for tolerance. So recently, I've been using the 100k stereo pot in a box with RCA jacks. It ain't optimum, but it works pretty good really, provided the cables are shielded and short. Some day I'd like to invest in a transformer type of volume control from the likes of Intact audio or sumthin'.... The Altec 345A has left and right 100K volume pots right after the input jacks. I'll use some 100K type J Allen Bradley pots I have on hand. I can just input the CDP direct into the Altec amp. I do have a bone stock, and I mean bone stock factory wired 1959 Eico HF-85 pre-amp. It sounds ok, but it's a hum monster. I could go through it and modify/restore the unit, and improve upon it, but it's a clean piece of audio history and I don't wanna touch it......Besides, I thought my 6SN7 Aikido linestages sounded better. Mike

I've made it pretty much to layout and wiring. It should be a good sounding EL-34 PP amplifier provided I don't destroy it......

I bought my pair of SVS 16/46 CS series almost 8 years ago. Almost got a 700 wpc Behringer amp off CL the other day for them, but the douche pussed out on me. I guess I'll clean and rebias the old NAD 2100 power envelope one more time......

What kind of Yamaha speakers are they?

http://www.accuphase.com/index.html Bummer they don't have A/V receivers.

Think of that amp like a donkey........you load him down enough and he'll just sit there.......